I have used a Schwab index fund, many Vanguard funds, and lots of Vanguard ETFs. They all have benefits in one way or another. See this Wiki article link: ETFs vs Mutual Funds
While it is such a personal choice, sometimes which one is used is dictated by the vendor you have your account at. I will just say that nowadays one should not have to pay a commission for any fund nor ETF. If you do, then move your account.
Personally, I prefer mutual funds for bond funds and ETFs for equity funds although I do have equity mutual funds and bond fund ETFs. For me the biggest difference is how distributions and dividends are automatically re-invested.
I just cannot get used to the way dividends from ETFs are automatically re-invested. Unlike mutual funds were there is no friction and the drop in NAV gives one a corresponding increase in shares with no loss of value, for ETFs the re-investing process is more complicated. The distribution appears a few days after the share price has dropped (on the ex-dividend date) and the broker has their own mysterious method of buying new shares for you with your dividend. Sometimes you pay a higher price than the mutual fund investor would pay and sometimes you pay a lower price.
So while I have 4 different brokers, if I had a Schwab account, the first thing I would do is move my money from them. Sorry Chuck!
It's all about short-term opportunistic rebalancing due to a short-term change in one's asset allocation, uh, I mean opportunistic rebalancing, uh I mean rebalancing, uh I mean market timing.