When the underlying exposure is genuinely similar, choosing between them is not about which investment theme is better. It is about which vehicle delivers that exposure most efficiently. This article provides a structured framework for comparing nearly identical ETFs.
Key takeaway
When two ETFs offer the same index exposure, compare MER, tracking difference, bid-ask spread, fund size, and distribution frequency. No single factor dominates; the relative weight depends on holding period and tax situation.
This is general educational content, not personal financial advice or a recommendation of any specific fund. Individual circumstances vary. Due diligence on any investment requires reading the product disclosure statement.
Why "Nearly Identical" Is Not the Same as "Identical"#
Before comparing ETFs, it is worth confirming they are actually tracking the same thing.
Two ETFs may both be described as "global equity" or "Australian shares" while tracking different indices with meaningfully different compositions. For example:
- An ETF tracking the MSCI World ex-Australia index includes developed markets excluding Australia
- An ETF tracking the MSCI ACWI ex-Australia includes both developed and emerging markets
- An ETF tracking the FTSE Developed World ex-Australia index has a similar composition to the MSCI World but with different constituent and weighting rules
These are not the same exposure. Before running a cost comparison, confirm what benchmark each ETF tracks and whether those benchmarks are materially similar in composition, geographic weighting, and sector allocation.
The comparison framework below applies to ETFs that genuinely track the same or substantially similar indices.
The Comparison Factors#
1) Management Expense Ratio (MER)#
The MER is the annual fee charged by the fund, expressed as a percentage of net assets. For a passive index ETF, it is the most visible cost and the starting point for comparison.
For funds tracking the same index, a lower MER is generally better, all else being equal.
However, MER alone does not capture the true cost. Two funds with identical MERs can deliver different net returns if one replicates the index more or less efficiently.
What to check: The fund's PDS or the ETF provider's website will state the management cost or MER. Make sure you are comparing the same metric (some providers quote management costs that include additional costs; others quote only the base fee).
2) Tracking Difference#
Tracking difference is the actual gap between what the ETF returned and what its benchmark index returned over the same period.¹
Unlike MER, tracking difference captures the total impact of all costs and efficiencies: fees, trading costs, cash drag, securities lending income, withholding tax drag, and dividend timing differences.
A fund with a higher MER can sometimes have a better (smaller) tracking difference because it earns offsetting income through securities lending.
What to check: Annual fund reports and fund manager performance pages. Compare the ETF's stated return for a full calendar or financial year against the benchmark index return for the same period. Tracking difference = ETF return − Index return.
A negative tracking difference (ETF underperforms the index) is typical and should be roughly in line with the MER. A tracking difference significantly worse than the MER suggests additional unaccounted friction.
3) Bid-Ask Spread#
The bid-ask spread is the difference between the buy and sell price at any moment. It represents an implicit transaction cost every time you trade.
For a buy-and-hold investor who trades infrequently, the spread is incurred at entry and exit only, so its impact is minor. For an investor using dollar-cost averaging and buying monthly, spread costs accumulate and become a more meaningful total cost factor.
What to check: During mid-session ASX trading hours, open the ETF's order screen and note the bid and ask prices. Calculate the spread as a percentage of the midpoint (spread ÷ midpoint × 100). Compare across funds.
ETFs with higher trading volumes typically have tighter spreads due to more active market maker competition.
4) Fund Size (Assets Under Management)#
Larger funds generally (though not always) benefit from:
- More active market makers competing for trades, producing tighter spreads
- Greater operational efficiency in index replication due to scale
- Reduced risk of the fund being closed due to insufficient commercial viability
A very small ETF (for example, below $50 million AUM) carries closure risk. If a fund is wound up, investors would typically receive their pro-rata share of the underlying assets (a capital gain event) at a time not of their choosing.
What to check: The fund's ASX product page or provider website will list the fund's AUM. Compare across similar funds.
5) Securities Lending#
Some ETFs lend their underlying securities to short sellers and earn income from this lending. This income can partly or fully offset management costs, resulting in a better tracking difference than the MER would suggest.
Securities lending introduces a small degree of counterparty risk (the risk that the borrower fails to return the securities). Reputable ETF providers mitigate this through collateralisation and conservative lending programs.
For most investors comparing retail-accessible Australian ETFs, the difference in securities lending income between comparable funds is small. It is worth noting in the comparison but rarely the deciding factor.
What to check: The fund's PDS or the annual report typically discloses whether securities lending is conducted and the estimated benefit.
6) Distribution Frequency and Structure#
Australian ETFs distribute income at different frequencies: some quarterly, some semi-annually, some annually.
For most investors, distribution frequency is a secondary consideration. However, it matters for:
- Tax timing: annual distributions concentrate taxable income in a single financial year. Quarterly distributions spread it.
- Reinvestment efficiency: quarterly distributions can be reinvested more frequently, compounding at a slightly higher frequency.
- Cash management: investors who draw income from their portfolio may prefer quarterly distributions.
The tax treatment of distributions also varies. Whether a fund distributes primarily dividends (with attached franking credits) or capital gains can affect the tax efficiency for specific investors.
What to check: The PDS will state distribution frequency. Historical distribution statements show the composition of past distributions.
7) Fund Domicile#
For ETFs providing international exposure, where the fund is legally domiciled affects the withholding tax rate applied to dividends from underlying holdings.
An Australian-domiciled ETF holding US shares accesses the Australia-US double tax treaty rate (typically 15% withholding on US dividends). An ETF domiciled in Ireland accessing the Ireland-US treaty may pay a different rate.
For Australian investors, a domestically domiciled international ETF is generally simpler from a tax reporting perspective and typically avoids the US estate tax risk that can apply to investors holding US-domiciled funds directly.²
What to check: The fund's PDS will state the domicile. For global equity ETFs listed on the ASX, most are Australian-domiciled.
A Weighted Decision Matrix#
Use the following template to score two or more comparable ETFs systematically. Assign a score from 1 (worst) to 5 (best) for each factor, then multiply by the weight column.
| Factor | Weight | ETF A | Weighted A | ETF B | Weighted B |
|---|---|---|---|---|---|
| MER | 25% | – | – | – | – |
| Tracking difference (1-3 yr) | 30% | – | – | – | – |
| Bid-ask spread | 15% | – | – | – | – |
| Fund size (AUM) | 15% | – | – | – | – |
| Distribution frequency/type | 10% | – | – | – | – |
| Securities lending | 5% | – | – | – | – |
| Total | 100% |
Adjust weights based on your situation:
- Increase tracking difference weight for long holding periods (it compounds over time)
- Increase bid-ask spread weight for regular investment via DCA (the cost is incurred repeatedly)
- Increase distribution frequency/type weight if tax efficiency in a specific account type is a priority
No single answer emerges for all investors. The matrix makes trade-offs visible and explicit.
Where to Find Data#
| Data Point | Where to Look |
|---|---|
| MER | ETF provider's website, PDS |
| Tracking difference | Annual fund report; calculate manually from ETF return vs index return |
| Bid-ask spread | ASX trading screen during mid-session |
| AUM | ETF provider's website, ASX product listing |
| Distribution history | Fund manager's distribution page, ASX announcements |
| Domicile | PDS |
| Securities lending | Annual report, PDS |
The Factor That Often Matters Most#
For a buy-and-hold investor holding a fund for ten or more years, tracking difference is often the most material factor because it compounds across the holding period. An ETF with a 0.05% p.a. better tracking difference than a competitor will produce a meaningfully different outcome over a decade compared to one-time factors like a slightly wider bid-ask spread.
For an investor using regular monthly contributions, bid-ask spread is elevated in importance because it is incurred with every transaction.
For an investor who plans to draw income from the portfolio in retirement, distribution frequency and tax efficiency become more prominent.
The right weighting is not universal. It is a function of investment horizon, contribution pattern, and tax situation.
Summary#
Comparing nearly identical ETFs requires looking beyond the management expense ratio to the complete picture of cost and quality. The most important factors are tracking difference (which captures real-world replication efficiency, not just stated fees), bid-ask spread (particularly relevant for frequent investors), and fund size (which affects spread quality and viability risk). A weighted comparison matrix, with weights adjusted for your holding period and tax situation, is a useful tool for making the comparison explicit. No factor dominates in all situations; the goal is to find the most efficient vehicle for delivering your chosen exposure, given your individual approach to investing.
Sources#
- Morningstar. (2023). ETF tracking difference and tracking error. https://www.morningstar.com.au/investing/article/etf-tracking-difference-and-tracking-error/218244
- Passive Investing Australia. (2023). Fund domicile and avoidable US taxes. https://passiveinvestingaustralia.com/fund-domicile-and-avoidable-us-taxes/
- ASX. (2024). Exchange traded funds product directory. https://www.asx.com.au/markets/trade-our-cash-market/asx-etf-product-list