Hmm, I think Sam was trying to deal with his anger all the way through. It's just that he deals with anger by talking and Dean won't talk ("no chick flick moments"). Sam didn't really have anyone else to talk to most of the time so it wasn't surprising his anger built up. Dean's coping mechanisms are more suited to the hunter lifestyle I reckon.

Anyway, they're fictional characters, so interpretations vary. I personally would love more insight into their psyches but since the show is more about action, it's not gonna happen.