I absolutely agree with mvtoro that Utah has more personal fouls and unnecessary roughness calls.

I don't agree that nobody watches Utah. They outdraw BYU by a solid margin. That may well be because people are tuning in to see their opponents, but they would still see Utah play and, if anything, be more upset, with dirty plays from Utah.

I think the reason that BYU has a worse rep for being dirty is three-fold.

1) BYU was top dog in the WAC/MWC for a long time and therefore most disliked and developed the reputation back when people actually didn't care about Utah. Even if it's no longer accurate, reputations often exist based on past precedent.

2) Utah consistently is right at (or just past the line) so gets lots of smaller, less noticed infractions. BYU generally does better, but when they go over it's punching a guy in the nuts or a massive brawl, things that get more national attention.

3) BYU, representing the LDS faith, is held to a higher standard by a lot of people. So when a BYU player does something borderline dirty, people are more likely to notice and comment than if a Utah (or Texas or Nevada or Boise or Penn St) player does so.