Utah was the winningest program from the MW -- the best non-AQ conference, with the most wins versus BCS teams, the highest profile seasons, the most NFL draft picks (by far) and the only one to finish the top 10 with two different coaches (program sustainability).
That's a great resume. If you're looking at competitiveness, hard-pressed to find a better candidate.
BYU is a great program. Nothing to take away, but the program peaked in the 80s and in the WAC. It has sustained success in the BCS era and the MW clearly taking a backseat to the other two programs. TCU won the Rose Bowl! Utah beat Alabama!
That's a whole different level of accomplishment during the most critical era for expansion.
I believe most CFB fans would agree BYU is P5 worthy but almost no one outside of the BYU base would say they were more deserving than the other two.
The 1-7 record against UU/TCU doesn't help either.