Your question implies that (1) someone who I don't get along with but knows the work is possibly a good fit, and (2) someone who I get along with but who can't do the work is possibly a good fit. Why does it have to only be those two choices? I would say "They must be both" but that is such general advice for any situation that I doubt it is helpful.

This is a very general question that Google would do a great job of helping you answer. If you asked a more specific question(s), perhaps we could help more.