I'm not sure it was the fact Psycho has more of a personality than Nomad, or the fact it takes place (starting) about halfway through Crysis, and finishes just before the end of Crysis (so in both games the aliens are just short of being revealed, cutting out a lot of the Korean punishing that is the first half of Crysis), but I felt Warhead was a superior game, the only letdown being it wasn't as long.