That would depend on the team, I think. Emerald is good for him in that it encourages his more positive traits, even if it also encourages his tendency toward self-sacrifice, which can be bad as well as good (and makes Sasuke cranky). I've speculated with Saro that Iolite would have encouraged his more negative traits, like ninja ruthlessness and amorality and manipulation. Vincent would have been a negative influence the way KK is a good one.

Same question for Mukuro.