I'd have to go with Itachi. Everyone knows that hes badass and all, but his spiritual weapons give him the upperhand in just about any fight. Plus no ones what Kabuto can do. Sure he has Impure World, but what else does he have. Although he has Oro's power I dont consider him an upgraded version of Oro. I think Oro is still way better than Kabutomaru, in both intellect and strength.