Just a few subtle points (which you may have already discovered from bogleheads):
1. You pay the bid/ask spread when buying/selling ETF's. Thus, there is an extra "hidden" fee to trading ETF's that doesn't exist with Mutual Funds. For heavily traded ETF's (i.e. those with high daily volumes), the bid/ask spreads are very small; but be careful of ETF's with low volumes. VTI should be fine. Then again, you could think of this "hidden" fee as what you pay for more flexible buy/sell features (e.g. limit orders, market orders, etc..).
2. Depending on your broker, you may not be able to do automatic, periodic purchases of ETFs. Thus, mutual funds may provide an easier time for establishing a "set and forget" automatic contribution (for DCA strategy).
3. Along the same lines as #2, you may not be able to automatically deposit dividends into an external account (but instead only a "sweep" account, like a money market fund). Perhaps that's okay, but perhaps not what you want :).
4. With Vanguard, you can convert an admiral class mutual fund (like VTSAX) into it's ETF equivalent (like VTI). Note, you may have to have your funds invested directly with Vanguard to be able to do this.
So, the bottom line is ... go with ETFs if:
1. you want the extra flexibility around buying/selling (i.e. the ability to do intra trading-day orders, instead of only end-of-day order at NAV)
2. you are investing a lump sum and don't have enough for admiral class shares (since ETFs give you admiral class fees at any quantity).
Otherwise, you should probably go with Mutual funds. If you are using Vanguard directly, and you change your mind later, then you can always convert existing funds you own into ETF equivalents.
If you are unsure about any of the above points, just go with the Mutual funds :)