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Index ETF or Index mutual fund - standard brokerage account
The main difference between a mutual fund and an ETF are how they are bought and sold (from the investors perspective). An ETF is transacted on the open market. This means you normally can't buy partial shares with your initial investment. Having to transact on the open market also means you pay a market price. The market price is always a little bit different from the Net Asset Value (NAV) of the fund. During market hours, the ETF will trade at a premium/discount to the NAV calculated on the previous day. Morningstar's fund analysis will show a graph of the premium/discount to NAV for an ETF. With a mutual fund on the other hand, your investment goes to a fund company, which then grants you shares while under the hood buying the underlying investments. You pay the NAV price and are allowed to buy partial shares. Usually an ETF has a lower expense ratio, but if that's equal and any initial fees/commissions are equal, I would prefer the mutual fund in order to buy partial shares (so your initial investment will be fully invested) and so you don't have to worry about paying premium to NAV