It would make sense that if the other character is supposed to be the calm, leader type he should have higher charisma to keep his companion in check, no? If you're worried about optimization, one or two points into Charisma isn't going to break your character and enforces the role you seem to want him to have. Added benefit is that he'll be better at being the voice of reason against other NPC's as well.
I do recall there being an option to back out of the argument before the rock-paper-scissors thing is initiated, but I don't recall if it's for both companions or just the one who initiates the conversation.
