I've barely touched PLD, as for the others... I'd probably rank them GNB>WAR>DRK, which sucks because Dark Knight was what I was gunning for from the start but... idk, I think it falters compared to the other two in terms of actually playing it.

Gunbreaker and Warrior feel better both in terms of animations and sound effects and also like they've got more going for them, whereas with Dark Knight you spend a lot of your time with just the basic 1-2-3...