Both LES and RES have some variety in elevation between different gates and field surface etc.
Using an elevation tool, it appears that highest ground level of any point of the stadium is about 5 ft higher for Utah than BYU.
But field level for BYU is about 10 feet below that, while for Utah it's about 25 feet below that - meaning BYU's field level is about 10 feet higher.
In any case, they're effectively the same