How to choose between ETFs that track the same index

Why are there many ETFs for the same index?

If you run a simple search for "S&P 500 ETF", you will see dozens of results: iShares, Vanguard, Amundi, Xtrackers.

Many ETFs can track the same index (such as the S&P 500), yet they differ in domicile, cost (TER), distribution type (accumulating or distributing), replication method, size and liquidity and trading currency; choosing the right one means matching these characteristics to your own situation.

🔶 But what is the reason behind this "multitude"?

The answer is simple, but it matters a lot for the investor: the fact that two ETFs follow the same index does not mean they are identical.

Each provider creates its own ETF based on the same objective, but with a different:

• structure
• tax treatment
• dividend class (ACC or DIST)
• currency share class
• size and liquidity
• cost (TER)
• listing exchange

So, although they all "track the S&P 500", in the detail they can differ significantly.

This is good news for the investor, because it creates choice.

Depending on personal needs (such as the country of tax residence, whether DCA is applied, the preference for an accumulating or distributing form, as well as the available platforms used) the investor can pick the ETF that best serves their own strategy.

Example: An investor in Europe may choose VUAA (Vanguard S&P 500 UCITS ETF Acc), while another may prefer CSP1 (iShares Core S&P 500 UCITS ETF Acc).

Both ETFs have exactly the same objective, namely to replicate the path of the S&P 500.

However, they differ in points that can affect the investor’s experience and final return.

They may have a different:

• TER, which affects the cost
• size and liquidity, which affect the spread and stability
• listing exchange
• tax treatment depending on the investor’s country of residence
• currency share class and structure

That is why choosing an "S&P 500 ETF" is not a one-way street.

It concerns details that over time can make a real difference, especially for investors who apply DCA or manage portfolios with a long-term horizon.

Are they all "the same"? The key points of differentiation

The most common misconception for those starting to invest in ETFs is that all products tracking the same index are identical.

After all, if both ETFs target the S&P 500, should they not perform almost the same?

In reality, however, there are differences that are not visible at first glance. These can affect performance, taxation, liquidity and the investor’s experience.

Below are the most important characteristics that differentiate two ETFs with the same underlying index:

1. Total cost (TER: Total Expense Ratio)

• The TER shows the annual management cost of the ETF.
• Although all companies try to reduce costs on their core ETFs, even a difference of around 0.05%–0.15% per year can make a significant difference to long-term performance, especially when compounding is applied.

Note: the TER does not include costs such as spreads, buy/sell commissions or any swap fees.

2. ETF domicile

• Most European ETFs are domiciled either in Ireland or Luxembourg.
• This difference is not merely geographical or legal: it has real tax consequences.
• Especially for ETFs investing in US equities, Irish ETFs have the advantage of lower withholding tax on dividends (15% instead of 30%), due to a bilateral treaty.

Over time, this difference translates into a higher net return for the investor.

3. Distribution type: Accumulating or Distributing

An ETF can:

• Reinvest dividends automatically (accumulating)
• Distribute dividends to your account (distributing)

The choice between the two is not just a matter of preference.

It has tax implications, differences in how it performs long-term and affects whether it fits your strategy, especially if you follow a DCA strategy.

In some countries, for example, dividends are taxed immediately, while reinvestment "defers" them for tax purposes.

4. Replication method

ETFs are distinguished into:

• Physical replication: they actually buy the index’s securities
• Synthetic replication: they use swap contracts to mimic the return

Most large ETFs (such as those for the S&P 500) use physical replication. However, synthetic ETFs still exist, mainly for more difficult or less liquid indices.

Investors should know the differences, mainly on transparency, tracking error and counterparty risk.

5. Size and Liquidity

• An ETF’s size (AUM) and its liquidity have a practical impact.
• The larger the ETF, the greater the likelihood of low bid/ask spreads, better daily pricing and stability.
• A small or "unknown" ETF may have higher transaction costs, mainly due to an increased spread.

6. Trading currency and conversions

• Some ETFs are listed on more than one exchange and in different currencies (EUR, USD, GBP, etc.).
• This can cause extra conversion costs from your broker or lead to a mismatch between the ETF price and your portfolio currency.
• In addition, some ETFs offer currency hedging (i.e. cover against currency risk), something you should know before investing.

🔶 Why two ETFs with the same index are never really the same

• Two ETFs tracking the same index are never really "the same".
• They differ in cost, tax efficiency, distribution strategy, size and many other characteristics that can materially affect your long-term investment.
• If you ignore these details, you risk choosing a product that does not serve your needs or goals.

Careful ETF selection is part of your investment strategy itself.

Accumulating or distributing: How it affects your return

One of the most important choices when picking an ETF is whether you choose one that reinvests dividends (accumulating) or one that distributes them to your account (distributing).

Although these are two technically simple concepts, their consequences are multidimensional: tax-related, investment-related and psychological.

🔶 What does "accumulating" mean in practice?

An accumulating ETF does not pay you dividends. Instead, it reinvests them automatically inside the ETF itself.

Thus, the ETF’s share value rises with the dividends that are not distributed, while compounding works without friction or taxes (at least directly).

This means:

• You do not need to reinvest manually
• You do not receive "cash flow", but the value of your ETF increases
• Taxation (in many countries) is deferred until you sell

🔶 What does "distributing" mean in practice?

A distributing ETF distributes dividends to its shareholders, e.g. quarterly.

This option is ideal for those who want regular income or for more passive investors who wish to live off their portfolio (e.g. in the "financial freedom" phase or during retirement).

However, it also means:

• Immediate taxation of dividends in several European countries
• If you want to reinvest them, you must do so manually
• Returns appear smaller if you do not account for the dividends

🔶 Which is more efficient over time?

In theory, if you reinvest all dividends correctly, immediately and at no cost, the final return of an accumulating ETF and a distributing ETF would be essentially the same.

Both track the same index, so the difference arises solely from the way they handle dividends.

In practice, however, accumulating ETFs show a slightly higher return over time, for three very specific reasons:

• They benefit from compounding without intermediate tax charges. In many countries the dividend is not taxed at the moment it is generated inside the fund. This means capital grows uninterrupted and compounding works at maximum strength.
• They avoid mistakes or delays in reinvestment. With distributing ETFs the investor must reinvest manually. In practice this rarely happens on the same day, at the same price or with absolute consistency.
• They do not depend on the investor’s discipline. The human factor introduces delays, strategy changes or even the complete absence of reinvestment. With accumulating ETFs the process is automatic and leaves no room for error.

These small practical differences accumulate over the years.

And over a long horizon, this seemingly small divergence can develop into a significant advantage in favour of accumulating ETFs, especially for investors in the accumulation phase seeking clean, long-term growth.

🔶 Does your country of residence matter?

Yes. Your tax residence determines whether you will pay tax on dividends, when and how much. For example:

• In some countries, accumulating ETFs are not taxed until you sell
• In others, tax applies even without dividend distribution (e.g. through deemed distributions)
• At fund level, Irish UCITS ETFs are not charged additional tax on the dividends and capital gains generated internally; the taxation of the investor, however, depends on their country of tax residence.

That is why many European investors choose accumulating ETFs, especially when doing DCA.

🔶 Which option fits you?

The choice between an accumulating and a distributing ETF is not a matter of "right" or "wrong". It is a matter of needs, goals and personal investment style.

Based on what you want to achieve and how you manage your money, the answer can be entirely different.

ETF domicile and tax implications

Most European ETFs are domiciled either in Ireland or Luxembourg, two countries that offer a favourable framework for funds.

This choice is not made randomly by the issuers: it relates to bilateral tax treaties and to how the dividends the ETF receives from third-country companies are taxed.

The most important case is dividends from US equities (e.g. in ETFs tracking the S&P 500, Nasdaq, etc.).

• Irish ETFs benefit from the US–Ireland tax treaty, with a 15% withholding tax on dividends
• Luxembourg ETFs do not have a corresponding treaty and are subject to a 30% withholding at source (US)

This means that, without you doing anything at all, an Irish ETF can have up to 0.30% per year better net return purely because of the reduced withholding tax.

Example:

• Suppose two ETFs track the same index (S&P 500): one is domiciled in Ireland and the other in Luxembourg.
• The US tax withholding makes the second one "start" at a disadvantage, even if they have the same TER.
• Over a 15–20 year horizon, this difference can create a significant divergence in the final value of the invested capital.

🔶 How does this affect you as an investor?

• If you are a European investor buying UCITS ETFs through a European platform, it is good to prefer ETFs domiciled in Ireland, especially for US exposure
• The choice also affects the return calculation in comparison tools.
• Some aggregators do not always capture the tax difference correctly, resulting in underestimating the net return of an Irish ETF.
• If you do DCA into an ETF with US exposure, the slightest difference in return from tax treatment can accumulate significantly.

Cost comparison – TER, bid/ask and other “hidden” fees

When you first look at an ETF, it is easy to focus exclusively on the TER (Total Expense Ratio).

Indeed, it is the most prominent cost metric. Rightly so, since it includes all operating expenses automatically deducted from the ETF’s net value on an annual basis.

However, the TER is only the start. In practice, the real cost of owning an ETF can be higher, depending on how and when you buy or sell it, the platform you use and the ETF’s liquidity.

🔶 TER: What it includes – and what it does not

The TER covers:

• Management fees
• Operating expenses of the fund (audit, legal support, custody, etc.)
• Licensing costs for the use of indices (e.g. "S&P 500")

But it does not include:

• Buy/sell costs on the exchange
• Spreads (the difference between the buy and sell price)
• Currency costs
• Broker commissions

🔶 Bid/Ask spread: The often underestimated cost

Every ETF traded on an exchange has two prices:

• Bid: The price buyers are willing to pay
• Ask: The price sellers ask for

The difference between the two is the spread, which you pay indirectly every time you buy or sell.

For ETFs with high trading volume, the spread can be negligible (0.03%–0.10%), but for ETFs with low liquidity or smaller AUM, it can exceed even 0.50%.

This is a one-off cost, but if you trade frequently or do DCA with small amounts, it can have a bigger impact than you think.

🔶 Currency and conversion cost

If the ETF you buy trades in a currency different from your base currency (e.g. a USD ETF through a EUR account), then your broker will probably perform an automatic currency conversion, usually with a fee of 0.20% to 1.00%.

This cost often does not appear clearly anywhere, but it directly reduces the net value of your investment.

🔶 What affects spreads and the "real" cost?

Spreads are one of the most misunderstood yet important cost components when you buy an ETF. They do not appear as a commission in the transaction, but they directly affect the final price you pay.

To know what a purchase really costs, it is useful to know what determines the spread and how you can limit it.

• The size of the ETF (AUM). Larger ETFs usually have much lower spreads. This is because they attract more investors, so there is greater activity and a smaller gap between the buy and sell price.
• Daily liquidity. The more transactions occur in an ETF each day, the more "fair" and competitive the buy and sell prices are. High liquidity reduces the chance of paying more than the fair market price.
• The exchange on which it trades. Not all European exchanges have the same quality and trading volume. For example, Xetra in Germany usually offers tighter spreads compared to Euronext or other markets with lower liquidity. Choosing the right market can significantly reduce the cost.
• The time of trading. For ETFs based on US indices, trading outside US market hours can lead to "inflated" spreads. The reason is that the underlying stocks are not trading at that moment, so the ETF price is based on less accurate signals.

👉 Prefer to trade when the US market is open, especially for S&P 500 or Nasdaq ETFs.

Liquidity and size – Do they matter for you?

When an investor evaluates an ETF, they often pay attention to the index it tracks, the cost (TER) or the dividend distribution type.

However, two more important parameters directly linked to your experience as an investor are the ETF’s size and its liquidity.

Although often ignored, these two factors directly affect the transaction cost, the ETF’s stability and also the probability that it remains available in the market long-term.

🔶 What does "size" mean in practice?

An ETF’s Assets Under Management (AUM) (i.e. the total capital it has gathered) is an indication of trust and acceptance by the investment community.

• Larger ETFs (>1bn €) are considered stable, mature and with a low risk of closing
• Smaller ETFs (<100m €) may have lower liquidity, larger spreads and a higher risk of closing or merging

If you do DCA with small amounts, this risk may not particularly affect you.

But if you intend to invest substantial capital or hold it for 20+ years, it is preferable to aim for ETFs with significant AUM and track record.

🔶 Liquidity: why it matters more than you think

An ETF’s liquidity is the degree of ease with which it can be bought or sold in the market, without a significant change in its price.

In other words, how "alive" its trading is. Low liquidity can cause:

• Large bid/ask spreads (i.e. higher cost for you)
• Delays in order execution
• Unstable pricing (i.e. prices that deviate from the real NAV)

In ETFs with large size and high daily volume (such as CSP1 or VUAA), these phenomena are rare.

By contrast, a niche ETF with low trading volume can be significantly more "expensive" in practice, even if its TER is low.

⚠️ Beware of misleading volume

The trading volume you see on a platform or on a specific exchange does not always capture the total liquidity of an ETF.

• Many ETFs are listed simultaneously on multiple European exchanges, each with a different ticker.
• So a low volume on Xetra does not necessarily mean the ETF has low activity. At the same time there may be increased volume on Euronext, Borsa Italiana or Switzerland’s SIX.
• The most reliable picture comes from tools that aggregate data from all markets, such as the provider’s site or platforms that display the aggregated trading volume in real time.
• This helps you avoid wrong conclusions about an ETF’s liquidity and correctly assess its real operation.

🔶 The role of market makers

Even if at the moment you place an order there are not many active buyers or sellers, the market does not "freeze".

Market makers step in to maintain liquidity and ensure the ETF can be bought and sold at fair prices.

Their presence is more effective when the ETF:

• has a large size
• attracts steady inflows and outflows
• trades frequently during the day

In these products market makers play a more active role, which helps reduce spreads and better align the ETF price with the value of the underlying index.

In simple terms, an ETF may look "quiet" on your platform, but in reality have excellent liquidity thanks to the coordinated action of market makers and the multiple markets on which it trades.

Example – The S&P 500 in practice

Before comparing ETFs "on paper", it is useful to see how they differ in practice.

Even when they track the same index, like the S&P 500, they can have different costs, different liquidity and a different tax structure.

The table below gives you a clear picture of the most popular options in Europe and helps you understand which product best fits your own strategy.

🔶 What we conclude from the table

• VUAA and SXR8 have a similar structure: both are accumulating, with physical replication and an Irish domicile, which makes them tax-efficient for European investors.
• SXR8 has a much larger AUM and an older issue date, while VUAA is often preferred for its simplicity, the Vanguard name and its clean strategy.
• Invesco’s D500 has the lowest TER (0.05%), but is distributing and uses synthetic replication, which can be seen either as an advantage (if you care about cost and cashflow) or a disadvantage (if you avoid derivative-based ETFs for risk or transparency reasons).
• All trade in EUR via XETRA, the leading ETF platform in Europe, with high liquidity.

🔶 How to use this information

If you are planning a long-term strategy with DCA, an accumulating ETF with physical replication and an Irish domicile will most likely serve you best.

This category is tax-efficient for European investors, harnesses compounding without intermediate decisions and works excellently with steady monthly purchases.

In this case, VUAA and SXR8 are the two cleanest options. They offer high liquidity, transparency, a similar TER and different advantages depending on what you prefer more:

• the Vanguard brand and simplicity (VUAA)
• the enormous size and stability of iShares (SXR8)

If instead you want regular income or are building an income-based strategy, then a distributing ETF like D500 may interest you more.

It is cheap, pays dividends and suits investors who want liquidity without selling units. As long as you are comfortable that:

• it uses synthetic replication
• dividends may be taxed annually (depending on your tax residence)
• its net return depends on how you handle the dividends

How to choose the right ETF for you

With so many options available for the same index, it is easy to get lost in details or to rely solely on "which is cheaper".

In reality, ETF selection should be based on who you are as an investor: where you are, what strategy you follow, what your time horizon is and what priorities you have.

Let us look at the basic steps that will help you choose correctly.

1. What is your tax residence?

The country in which you are taxed affects:

• Whether tax will be withheld on dividends (distributing)
• Whether there are advantages from the ETF’s domicile (e.g. Ireland vs Germany)
• When and how gains from sale or reinvestment are taxed

If you are a European investor and invest in US equities, prefer ETFs with an Irish domicile to limit the withholding tax on dividends.

2. Do you want to receive dividends or have them reinvested automatically?

If you do DCA and have a long-term horizon, accumulating ETFs allow you to harness compounding without paying tax every time an amount is distributed.

But if:

• You want to have regular income
• You do not want to liquidate capital
• Or you are in a "withdrawal" phase

then a distributing ETF may fit your case better.

3. Cost matters, but not only the TER

Look for:

• TER below 0.15% (ideally <0.10%) for core ETFs
• Liquidity: trading volume, AUM >1bn €
• Bid/Ask spread: the smaller, the better

And do not forget to account for:

• The currency costs, if you trade in a different currency
• Your platform’s commissions

If you make frequent purchases or small DCA amounts, the total transaction cost matters more than you think.

4. What is your investment horizon?

The time horizon is one of the most decisive factors in choosing an ETF.

It affects not only the level of risk you can take but also which type of ETF will work best for you over time.

Long-term horizon (>10 years)

• If you invest with a decade-plus goal, you have time to fully exploit the power of compounding.
• In this case accumulating ETFs are usually more efficient because they maximise growth without intermediate decisions.
• At the same time it matters to choose low cost and tax efficiency, since these two elements directly affect the final outcome.

Medium-term horizon (3–10 years)

• In this time range your priorities change.
• Liquidity and cash flow may gain greater importance, especially if there is a chance your needs change.
• You can combine an accumulating ETF for growth and a distributing ETF for greater flexibility depending on the goal.

Short-term horizon (<3 years)

• For such a short period ETFs may not be the right tool, especially if you are exposed to volatility.
• Markets do not always follow a smooth path and the short-term investor is more at risk of being affected by sharp fluctuations.

The investment horizon also affects whether it is worth "chasing" the ideal ETF or whether a product that is reliable, easily accessible and efficient enough is sufficient.

The more distant your goal, the more value consistency, simplicity and tax efficiency have.

With a shorter horizon the priority shifts to flexibility and liquidity management.

5. Do you use DCA or invest as a lump sum?

The way you place your money in the market directly affects which ETF will serve you best.

DCA and lump sum are two different investment philosophies and each has its own characteristics.

If you use DCA

• DCA relies on steady, repeated investment.
• In this context accumulating ETFs work more smoothly because they let dividends be reinvested automatically and maximise growth over time.
• You do not need to track dividends or make extra moves.
• The process becomes simple, clean and especially disciplined.

If you invest as a lump sum

• In this case the key is not monthly consistency but correct allocation and the time horizon.
• You may be more interested in liquidity or the ability to receive dividends, especially if your goal is to use the cash flow.
• Here distributing ETFs can offer extra flexibility, while accumulating ones remain ideal for anyone who wants clean, long-term growth without needing management.

Overall, the method you use to place money in the market affects which type of ETF best fits your strategy.

DCA combines excellently with accumulating ETFs, while a lump sum can also justify using a distributing ETF, depending on your goal and needs.

Common pitfalls and mistakes when choosing an ETF

Choosing an ETF for the S&P 500 or the MSCI World seems like an easy decision: "just take the one with the lowest cost and we are done".

In practice, however, many investors make mistakes that cost them in performance, taxation or simply in investment experience.

Let us look at the most common ones and how to avoid them.

🔶 Choosing an ETF based on the name alone

• Many think that an ETF from a "big name" (Vanguard, iShares, Amundi) is automatically the best choice too.
• Although these providers do offer reliable products, it is not the name that determines performance or suitability, but the ETF’s characteristics.

It is common for an ETF to be preferred simply because "everyone has it", without examining the taxation, the dividend type or the platform on which it is available.

🔶 Indifference to domicile and tax consequences

• An ETF with a German or Luxembourg domicile investing in US equities loses up to 30% of gross dividends due to withholding tax, unlike Irish ETFs which benefit from lower withholding (15%).
• If you ignore this difference, it is like paying a "hidden tax" every year, something that is nowhere visible in the TER.

🔶 Choosing a distributing ETF without realising it

On some platforms or aggregators, it is easy to end up with a distributing ETF without knowing it, because it is not shown clearly in the product summary.

The problem is that you may:

• Be charged dividend tax you had not anticipated
• Needlessly disrupt the flow of compounding
• Need to reinvest manually every quarter

If you do not want cash flow but capital growth, explicitly check that the ETF is accumulating.

🔶 Focusing only on the TER without accounting for spreads

• An ETF with a 0.07% TER but a 0.30% bid/ask spread can be much more expensive in practice than another with a 0.10% TER and a 0.05% spread.
• If you do DCA or trade frequently, the spread acts like a "hidden entry cost" every time.

Most investors underestimate this factor, especially if their platform does not show buy/sell prices in real time.

🔶 Choosing an ETF that is not well supported by your platform

• Every broker has a different range of ETFs.
• If you choose an ETF that is not fully supported (e.g. does not trade directly or has high currency conversion costs), you may end up with complex orders, delays or increased charges.

Before deciding, see which ETFs are actually available and worthwhile through your platform.

🔶 Overlapping ETFs (without reason)

• Another risk is investing simultaneously in several ETFs covering the same index or almost the same assets, e.g. VUAA and SXR8.
• If there is no specific reason, this does not offer diversification: it only adds complexity.

A "clean" choice of one core ETF with the right characteristics is more effective than a mosaic of repeating products.