Povetkin handily in my opinion. He was bigger, busier, more skilled and had if not quite a Merceresque chin, a pretty darn good one. In my opinion he'd beat Mercer comfortably on points in what would be an entertaining fight.
This, if you sit there an trade with Mercer you're a fool and he'd have a good chance at clipping you. Povetkin had the ability to outbox Mercer (which was definitely possible), I don't think he'd even take the chance. No chance he's stopping Mercer though
I agree with those who picked Povetkin on points. I liked Ray Mercer but Povetkin was both more skilled and more disciplined. This isn’t a knock on Mercer at all who had a ton of heart and was in some great fights but the chemistry is wrong for him here