Very tough one to predict. They're both massive punchers, real knock out artists. My guess is Carwin is probably the bigger puncher....all his wins have been in the first round...he's also got a wrestling background which may help, although he doesn't use it much.
Dos Santos doesn't seem to have much of a ground game, although I don't think it will matter in this fight, they'll both stand and slug. Carwin has some health and fitness question marks. I hope Dos Santos wins, but I woudn't be surprised if Carwin knocks him out.