Have played Jedi Consular to lv 25, trooper to 20, BH 50, Sith Warrior to 42 (currently playing)
I stopped play both Rep characters because of the really boring storys up to their level's.
*side note: Both Rep are females, while both Empire are male*
The BH were extremely fun up to 40-ish, then it started to get less interesting, or be more specific. After Belsavi it got less fun.
Sith Warrior - little less fun then BH up to when you become Lord, Then it gets better! *no spoiler*
The companions play a nice part in this aswell. Both SW and BH gets interesting and enjoyable companions.
My side of it so far.