Which one is most viable at endgame PvP and PVE?
Which has the best story?
Which is the best for leveling?
Which is easiest for a rookie healer?
And above all, which is most fun?
IF it was Imperial side...
If you mean easiest for a rookie healer to heal = pyrotech powertech
If you mean easiest to play as a rookie healer = bodyguard mercenary
BH story is one of the best
Leveling is balanced; you don't die often, but you don't burn through mobs that fast
Both are valuable in PVP and can hold their own in PVE
Same goes for republic side mirrors, except trooper story is bland like most republic-side stories.