I don't think John Peters and Melvin Crispell know a lot of theory, or at least that what I felt from watching their videos. This may be different now, since the videos are old. They do have VERY strong ears, and I'm sure they can listen to a song one time, then pop out their own version on a whim. I admire both of these guys, and have been looking up to them since 1993!
Knowing either is good, but knowing both is definitely better.
A theory person can't really come to a person that has a good ear and say, "You need to learn this." It won't work. From my experience, it'll always be the case that they feel you're the novice and should be getting lessons from them. This may not be the case with this dude, though. That's why I said just do your thing, and when you and the bass player are jamming; you're giving progressions and the bass player is able to follow, but this other guy is stumbling, he'll either want to learn, or get worse and start trying to outplay you guys. You should know his spirit better than me, and probably know which he'd do.