I tend to favor the baseball stadiums just because they seem to be more unique than most football stadiums. I like asymmetrical stadiums with odd sightlines, weird seating, etc.
I like the total experience at Oriole Park in Baltimore even though we were Nats fans and mostly attended games at Nationals Park when we lived in that area.
But for most bang for your buck, I thoroughly enjoyed Isotopes Park in Albuquerque and Bricktown Ballpark in Oklahoma City. They are beautiful parks in great settings with enthusiastic crowds. Combine all that with cheap tickets and a very hassle free experience, and I loved it. Those are the only AAA parks I've experienced, but if that is the norm, then I highly recommend everyone take in some AAA games.
As for college football, I dont know which non-WB stadium is my favorite, but I will say I thought the stadium and gameday experience at Penn State was the most overrated one I've attended. For 106,000 fans, it really wasnt all that loud or exciting. They'd crap their pants at a Tiger stadium night game.