Shimano XT and Avid are easy to find. I have both, Avid is in the way better looking the levers seem more compact, but Shimano has better leverage.
You can find great deal used because many has upgrade theirs and go disc brake. To answer your random q, yes rim makes a difference, if you have ceramic rims they would have better braking performance than standard alloy.
You can find great deal used because many has upgrade theirs and go disc brake. To answer your random q, yes rim makes a difference, if you have ceramic rims they would have better braking performance than standard alloy.