They are literally the same fund. Different share classes of the same, underlying Vanguard fund. If you have at least the minimum $3K buy-in for the mutual fund, it is six in one, half dozen in another.

That said, I would suggest the mutual fund as the better choice because: a.) mutual funds are designed for fractional shares, so you never have a few dollars of uninvested money sloshing around like you would if all your investments were full shares of an ETF, and b.) mutual funds only post an updated NAV once a day after the markets are closed. If you are the sort of investor that monitors your investments too closely, seeing the ETF dropping in real time can be disconcerting. You probably should choose the mutual fund.