I would argue they've both been irrelevant for almost 20 years. I think the ACC will spend it's basketball money to pay for some good football programs. Miami is often believed by their fans to be a good program if not a good team.
When was Clemson a powerhouse? When they could pretend that being undefeated in a poverty conference meant something. I feel the same way about the pac-10 except they have been showing more parity since the money could legally flow. I think it's easy to go into the post season well rested when a team doesn't play anybody.