I don't know about Cooper. In my opinion, Warmack and Warford are both better players from what I've seen. Cooper has big problems with the bullrush from strong, stout defensive tackles (he really did struggle against Sheldon Richardson and Dominique Hamilton in the bowl game against Mizzou; it was one of the only games that Richardson had any sort of impact, to be honest). He also had some struggles pulling against Mizzou's fast outside linebackers and defensive ends (Zaviar Gooden and Andrew Wilson gave him a lot of problems with their closing speed, and it caused a lot of tackles for a loss; both of them had excellent games. All in all, UNC didn't get a ground game going in that game. Every bit of damage they caused was done through the air.) Pass protection was good, but again, he struggled with bullrushes and faster ends like Michael Sam and Jacquies Smith lining up on the inside.
Maybe he improved this year, but from what I saw (which admittedly wasn't much), he was one of the most disappointing players in the Independence Bowl (aside from almost all of the UNC defense).