What are the benefits from each charm as they level up? Why wouldn't a Monk want to use Brawler?
Because in the end, you'll want the charm that affects your strike augs that you'll eventually need to outfit your team with. Since sorc's charms affect spell damage, that's the one you want(besides UC of course). I have an 11 Sorc on my Monk and with a NinjaV he procs 13k non crit, for example.