[Preem]

If you're planning to invest in more than one fund, then Vanguard mutual funds might be better since they don't charge sales commissions (although, depending on the size of your account, they might charge you an annual maintenance fee).

ETFs charge a commission every time you buy or sell them, just like a stock, unless your broker waives the transaction costs (which most don't).

If you're only going to purchase one fund, hold it for a long time, and not make frequent, period additional purchases, then it's a toss up.

Vanguard won't charge you a commission when you purchase their mutual funds, whereas purchasing ETFs will cost you a commission for each purchase/sale. But ETFs generally have lower management fees than mutual funds, so over a long period of time, ETFs might be the better choice.

Vanguard offers both mutual funds and ETFs, so the only reason for going with E*Trade would be if you wanted to purchase non-Vanguard ETFs, since E*Trade's transactions costs are lower.