I would say dropping a level makes a difference, though the player will still get to the NBA. It hurts development (you're playing against slightly less talented competition) and you're less likely to blow up as much, publicity-wise, as you would at a school like OU. Would Trae have gotten as much attention at UTEP? I don't think so (and I'm not sure he would have gotten more at UK -- I'm not sure it's possible to get more attention than he got at OU).
Would be Buddy have been Player of the Year at UTEP? Almost certainly not. One could argue that for a top-line player, a school like OU (and the other schools you mentioned) gives a five-star player the best of both worlds -- he get to be THE top dog at his school and if he really delivers on the court, he'll get all the publicity he could ask for.