👆 Maul's potential was great, but it seems he capped off way ahead of schedule, much like Anakin, due to the fact so much of him is now machine. As I said, it looks like the major difference is that getting refitted with mechanical limbs doesn't start you way back behind like it did in Legends - just that you now can't progress forward very much.
Further, while Vader is likely "more powerful" than Anakin as of his prime, assuming he starts off directly after ROTS with his power like it seems to be the case, that doesn't mean he's better. As we seen with Anakin in TPM and AotC, Luke in ESB and ROTJ, and Rey in TFA, your Force potential is a major factor in combat since it provides you with unnatural (even compared to the best of the best) reflexes and augmentation, especially in crucial moments. Thus, I'd favor ROTS Anakin over Vader in a contest, even if Vader can lift the heavier object, and I think the Emperor would too (especially if ROTJ Luke did beat Vader in a fair fight, which seems to be how the new Canon is heading).