Or maybe because the fight just started.I think the reason why Sasuke can't use the Rinnegan to the extant that Madara can is because Madara is way OP (Mokuton, Rinnegan, EMS). Sasuke has been injured/had near death moments like Naruto.
Regards to this thread's OP, I'd say Sasuke will never truly be at the power level Naruto is at because Sasuke isn't the Child of Prophecy (like Nagato was).