I don't value the combine nearly at all. The combine should never be the determining factor in deciding a players athletic ability. The combine should serve to confirm what you see or make you go back and watch again, but never to be the deciding factor.
Anyway, I don't view Barnett as a guy who will be the "next Suggs" or an elite edge rusher. I think he's going to get his dues with his super refined hand usage and motor that never quits, but when you can't change direction well and don't have great burst or quickness, you're just not going to do a ton of damage in the league as a pass rusher.
With Charlton, he's an athletic freak for someone his size. He's inconsistent as all hell and will require some serious coaching to really reach that ceiling, but he's got All-Pro potential written all over him. Will he ever reach that? I don't know. However, is he going to be a good starter anyway? I think so.
If I'm picking between the two, I'd take the upside if I know I'm getting a strong starter either way.