I gotta agree with Big Mac. It's 6 in one corner, 1/2 dozen in the other. I also have a TC4 and it's setup and balance is almost exact to the Yokomo (battery on one side, motor and elecs on the other).
The biggest difference I've seen between belt and shaft is who catches more rocks. I've honestly never seen either have issues. My Yok catches rocks like nobodies business. So, ever few minutes, I shake'em out and keep it moving. I've never seen a belt popping because of debris though. But, I've heard that it happens, and it makes sense.
If money isn't an issue, go with what you like more. Money and LHS support are the 2 biggest factors in people's choices (money being the biggest). But, if that isn't an issue, go with what you're comfortable with. Like I said before, there isn't a BEST really. I've seen quite a few chassis perform well with a good driver on stock set-up, just using tires.
You've actually got it pretty easy cuz you can get what you want.
Since LOSI's RTD kit just came out, I can't really comment on that as I don't know much about it. I think it's the XXX-S chassis or something like that. Not too sure.
i think i've said enough. i'm starting to ramble on.