Conor, no question. BJ may be the best lightweight of all time, in comparison to his peers at that time, but the game has greatly evolved and the fighters today are better. If you got a time machine and put UFC 205 Conor vs Penn that fought Sherk, Conor would win. BJ 'had more tools' but he wasn't a takedown artist and Conor's hands are just so good that he would control and TKO Penn, if not UD him Penn was a lot like Aldo in a sense, a black belt turned excellent stand up fighter, but they were designed to beat the wrestlers/style of the day.