Warriors have the best player, the experience, the better crunch time offense, home court advantage, and they are healthier at the moment.
Celtics have the best 5, the slightly better defense, and more size.
Celtics best chance is if the refs allow them to be really physical, and their biggest X factor is Smart. If the Celtics bring it and he's not shooting them regularly in the foot, then they will win the series. I am picking the Warriors because I think at least a few of these games are going to be close at the end, and the Warriors offense is good in crunch time and the C's have been manic.