If I am being honest, BYU had a bit of an attitude about the bottom of the MWC. Sometimes they were good, but there were programs that BYU really should always beat. I'm sure that everyone percieved that BYU felt that way, at least when BYU was good.
I can't name a B12 program that I really think BYU should *always* beat. B12 may not have a UT or OU, but every school cares about football and every school has enough fans, resources, and commitment to be dangerous and respected.
Also, #basketball. B12 is a great conference.