ASX investors who might like to use index funds to gain a broad exposure to all that the Australian stock market has to offer have two distinct choices when it comes to choosing said index funds. The most widely quoted index that covers our markets is the S&P/ASX 200 Index (ASX: XJO), tracking the performance of the 200 largest stocks on our markets.
However, the ASX's most popular index fund – the Vanguard Australian Shares Index ETF (ASX: VAS) – instead opts for mirroring the S&P/ASX 300 Index (ASX: XKO). This index, as you might guess, adds another 100 stocks on top of the ASX 200 for a more diversified product.
You can understand why many investors, especially those just starting out, might be a little confused about which is the better path to tread.
So today, let's look at the performances of index funds that track both of these benchmarks and see which ones come out on top.
ASX 200 vs. ASX 300: Is less more?
Before we get into the numbers, it's important to point out that, despite the ASX 300 having 100 additional shares compared against the ASX 200, this doesn't have a huge impact on either fund's fundamental makeup.
That's because both indices are weighted using market capitalisation. Not all holdings command an equal weight in either index. To illustrate, an ASX 200 ETF, as of 30 June, allocates 11.99% of its portfolio to the top holding, Commonwealth Bank of Australia (ASX: CBA). Its smallest holding – Nuix Ltd (ASX: NXL) – currently gets just a 0.02% slice of the pie.
Meanwhile, an ASX 300 ETF like VAS gives CBA a weighting of 11.62%. The smallest holding, Firefinch Ltd (ASX: FFX), gets 0.002%.
But let's get into some numbers.
Here's a table showing the performance metrics of the ASX 300-tracking Vanguard Australian Shares Index ETF against a popular ASX 200 ETF, the iShares Core S&P/ASX 200 ETF (ASX: IOZ), as of 30 June 2025. These returns include share price gains, as well as dividend returns:
| ASX index fund | 1-year Performance | 3-year | 5-year | 10-year |
| VAS | 13.67% | 13.30% per annum | 11.75% per annum | 8.79% per annum |
| IOZ | 13.77% | 13.50% per annum | 11.77% per annum | 8.70% per annum |
As you can see, it's pretty much a dead heat over most periods. The iShares ASX 200 ETF has come out on top over the past one, three, and five years, while the Vanguard Australian Shares ETF has the edge over the ten-year period.
Bear in mind that the Vanguard fund charges a slightly higher management fee today, 0.07%, compared to iShares' 0.05%. However, those fees have been higher in years past, so take that with a grain of salt.
Foolish Takeaway
This data shows, at least in my opinion, that choosing between the ASX 200 and the ASX 300 is a 'six of one, half-a-dozen of the other' choice. You can't really go wrong with either.
Personally, I have opted for an ASX 300 index fund in my own portfolio as I like the (very) slightly higher diversification it offers. But an ASX 200 fund is, in effect, just as good.
