I noticed Crawmerax is considerably harder to beat as a team (either that or he's quite easy for me to solo as a Siren), does he actually drop better guns when beaten as a team or does he just drop more of them?
he does. the more people you have in your game, the more loot and the better loot everything will drop. its halfway why i love to play the game with friends :D
Having a mod with +1 or +2 find rare items generally results in better loot than playing with another person without a plus to find rare, at least in my experience.
Mind you, having a team where everyone has a plus for find rare items (I've got ones for the hunter and the siren, not sure if ones for the others drop) would probably result in the best chance. :)