SLC market, BCS bowl wins, Institutional profile, BYU being Mormon are the biggest reasons in my opinion. Us being Mormon isn't the ONLY reason but certainly a factor since Stanford and Cal have made up their mind against religious institutions (real open minded and accepting, libs.)

Utah has merit and is more of a research based institution similar to most PAC schools. Utah is not "better" than BYU, just a better fit for the PAC profile.