I saw U2 in both banks. There was NO COMPARISON in sound quality. at (then) TCF Bank Stadium, it was fantastic. All in all perhaps the best concert I have ever been to (especially considering U2 is not my all time favorite band). We were sitting a long ways away and the sound was perfect - even during a rain storm.
We enjoyed it so much we jumped at the chance when U2 returned a few years later to play at U.S. Bank Stadium. It absolutely sucked. My wife always loved the warm up act (Beck) and the sound was so bad his set was half over before she even realized it was Beck.
I am told that U.S. Bank stadium seats that are lower and/or on the floor are better. But I can confirm anything higher on the sides in the Vikings stadium absolutely suck. It sucks so bad I have made a point of not returning there for a concert. I wouldn't think twice about a concert at the Gopher's stadium.