Take a look at the last 40 years:
Utah 19 wins
BYU 20 wins
Utah has won 14 of those games by 1 score or less
BYU has won 12 of those games by 1 score or less
The last 6 games each team has won has been by 1 score or less.
Even though BYU hasn't won in a few years, this is a rivalry by any accounts and a competitive one at that. In the last 20 years, only 3 games have been by more than 1 score. It seems to me that pretty much every game could have gone either way, make 1 play and the game's outcome changes.