considering their cd and hitrate buffs they arent bad..i went to cc once with a karma,plasma,ultimate,dende and i was turtle
we got to floor 40 pretty quickly with most of us having +6 armor and +8 weapons, although karma was having a pve oriented build with kid buu attacks and some other aoes from karma when pure majin couldnt be used so its damage output was about the same as plasmas (atleast the crits were nice 15% from turtle,22% from karma i think + weapons there were crits about 35k)
Both are good for PvP.
They have similar buffs that help them...but plasma is better for PvE & for supporting your team with the anti paralyze stun buff :)
i think that karma with pure maxed one pure majin atack is better than plasma ;ppp
and karma is much better dps with atk speed weapons and maxed buffs.
Plasma don't have powerfull aoe.