Like you said, one is good on mobs and the other good for 1v1.
Crusader: One BIG single number.
DK: Multiple good dmg.
Crusaders: Needs at least one orb to activate Finishers.
DK: Can use Buster or Thresher w/o charging. Buster is slower than a normal attack. Thresher is faster than a SB.
Depends on what you want...you're gonna get opinions from ppl, lil fact.
PS. Coma can be considered as a mobbing attack.
man...you really like polls?