Haden is very good. Sherman is good too, but he isn't as skilled as Haden. Sherman's height helps him a lot, but Haden is just a better cover corner IMO. I really like both of them a lot though.
If Claiborne gets his strength up to where it needs to be, he can be in that conversation with them. In particular, Mo has ball skills better than most corners and he simply has a natural knack for coverage.
Mo certainly will be a very good corner. The only question in my mind is will he be truly elite or will he just be very good. Getting Kiffin to coach him is going to really help him IMO, because he will really focus on fundamentals and make him be more of a technician. He has all the natural ability in the world... he just needed someone like Kiffin to help him reach it. Plus, young guys typically excel in Kiffin's system because it isn't as complex as some and they don't spend all their time thinking. They can just react.