Utah has outplayed BYU in BM's tenure? Bronco is 3-2 against Utah. Bronco has won 2 MWC championships, KWhitt has won 1. BYU has a better winning percentage overall and a better MWC winning percentage. BYU has also spent more weeks as a top 25 team than Utah during Bronco's tenure.
KWhitt did lead Utah to an undefeated season and a BCS bowl, that's the big difference. So I think any objective person would say that Bronco has been better than Whittinham on a year to year basis, but Bronco has yet to come up with a stellar season like like Utah did 2008.