Depends on the playstyle, Grey has the most utility and has the all mission menace class, Red is pretty fun for the aggressive player since it has most of the vamp toys(certain weapon and armor combos that red has are nigh one gal armies), Green is sorta the "safety" bet between the fairy, savior and bio-suit and its upgrade their isn't much you cant capture with ease, and you have the best healing and the best tank armor, Gold is the one i personally dont touch the things unique to it are just not as good as the other 3 imo