ETFs vs. mutual funds

Intraday trades, stop orders, limit orders, options, and short selling—all are possible with ETFs, but not with mutual funds.
 

ETFs and index mutual funds tend to be generally more tax efficient than actively managed funds. 

And, in general, ETFs tend to be more tax efficient than index mutual funds.
 

If you make regular deposits—for example, you use dollar-cost averaging—a no-load index mutual fund can be a cost-effective option, and it allows you to fully invest the same dollar amount each time (since mutual funds can be purchased in fractional shares).

When you buy or sell ETF shares, the price may be less than the net asset value (or, NAV) of the ETF. This discrepancy (aka: the "bid/ask spread") is often nominal, but for less actively traded ETFs, that might not always be the case.

By contrast, mutual funds always trade at NAV, without any bid/ask spreads.

People invest in actively managed mutual funds in hopes they'll surpass their benchmarks.

Also, actively managed funds acquired as part of a specific strategy may complement index funds in a portfolio, and help to reduce downside risk and mitigate market volatility.

Some markets are "highly efficient"—which means they’re so popular, there isn't much opportunity to add any real value via active portfolio management.

But in less efficient markets–like high-yield bonds or emerging markets–there may be greater opportunities through active portfolio management.