Went to a concert at AT&T Stadium last month. My friend was in floor seats, I was in the upper deck. She had an amazing time. I might as well have watched from home.
The screen is massive which helps, but the sound in the upper sections is delayed and echoey. Plus you're so far from the stage that the performer is literally a dot.
If you're going to a stadium show at Jerry World, splurge for floor or lower bowl. Upper deck is not worth it unless you literally cannot afford anything else.