BYU would beat Utah if they played now with all the Ute injuries. Utah doesn't have the personnel on offense to put points on the board against Bronco's defense without Booker or Covey. Also Mangum would pick apart their secondary of their banged up D. BYU will have to wait until next year though because Utah won't be in the Vegas Bowl.
But it's not debatable what team had the better season unfortunately. Utah beat seven P5 teams and BYU only beat one. Utah also had a top 15 SOS rating. BYU didn't have a top 50 SOS. Utah also beat Michigan and we know what happened to BYU there.
1-3 against the P5 isn't going to cut it folks. If BYU can beat a PAC-12 team in the Vegas Bowl it would make a big difference perception wise.