A mutual fund and an ETF can hold the identical portfolio and still be quite different products. The gap is in the plumbing.

How you buy them

A mutual fund is bought from the fund company. Orders are collected during the day and settled once, after the market closes, at that day's net asset value. Everyone who orders that day gets the same price.

An ETF trades on an exchange like a share. You can buy at 10:04 and sell at 10:06 at whatever the market offers, paying the spread each time.

For a long-term investor, intraday trading is a feature you will almost never use — and occasionally a temptation you would be better off without.

Costs

Index ETFs are usually the cheapest way to own a market, and this is where the historical gap has been widest. Traditional mutual funds — particularly those sold through advisors and banks — have often carried entry fees, higher ongoing charges, and sometimes trailing commissions paid to whoever sold them to you.

That said, the categories now overlap: index mutual funds exist with fees competitive with ETFs, and expensive actively managed ETFs exist too. Compare the actual funds, not the labels.

The structural advantage: in-kind creation

This is the part most articles skip. When large investors leave an ETF, shares are usually handed over in kind to an authorised participant rather than sold for cash. The fund therefore avoids realising capital gains, and those gains are not passed on to remaining holders.

A mutual fund facing redemptions has to sell securities, realising gains that can land on everyone still in the fund. How much this matters depends heavily on your tax jurisdiction — in some it is decisive, in others irrelevant — but the mechanism is a genuine ETF advantage, not marketing.

Where mutual funds still win

  • Automatic investing. Buying exactly 250 every month, fractions included, with no spread and no order to place, is genuinely easier — though many brokers now offer ETF savings plans that close this gap.
  • No temptation to trade. One price a day is a feature if you are prone to fiddling.

Summary

For most long-term investors a cheap index ETF is the default, largely on cost and structure. But a cheap index mutual fund with an automatic monthly plan you will actually stick to beats a perfect ETF you trade badly.