If you aren't DM'ing, then my suggestion is to play the class whose mechanics you dislike the least. Let the DM worry about XP and pacing, and let the other players worry about the aspects of their class you don't like.
Myself, I'm more of a take-it-or-leave-it DM, and would not cater to one or two players in particular; but I also have the good fortune to play with people that will accept all the warts of whatever system we're playing and try to have fun with it anyway (even if they grumble from time to time). After all, there is no perfect system that will please all players.