There are downsides to ETFs for sure. If you are consistently putting money in, you are paying a commission each time, not to mention the unseen bid/ask spread. Systematic investments in mutual funds do not suffer from these problems (assuming no load). For these reasons ETFs might not make sense in smaller accounts that are systematically investing. The expense ratio differences are not really big when you compare a passive ETF to a passive MF. The ETF advantage can be wiped out pretty quickly by bid/ask spreads. Edit: Just saw cv’s response which is pretty much the same.