MasterVegito 说:
Trainer and leadership are 2 skills that matter in this game for a companion, rest is irrelevant, since only those 2 do stack, once again, a genius move on developers part.
Right, like the other 12 skills are irrelevant to the player
Ignore this guy and read @Ivan great explanation about skills. Unless you cheat you will end up with several companions specialists (a doctor, a engineer, a trader, etc) that will make you better, besides having a elite group of immortal fighters with you. Companions rock.