Hard to say. Sasuke's still inexperienced with the Rinnegan which is shown when he cannot use Preta Path while using other jutsu like Nagato could and Nagato made better use of the Six Paths techniques than Sasuke did. However, Sasuke displayed more skill with Chibaku Tensei by having specific objects act as the core as well as creating a Gedo Statue and having a far superior Outer Path. He also can enhance his own Sharingan techniques with the Rinnegan and possesses an extraordinary S/T ninjutsu, so I would put Sasuke far ahead.
this for me. sure nagato used more paths but the few sasuke displayed, he used it better than nagato except preta
CT is a prime example. out of the 3 rin user to have used CT, sasuke is still the only one to have used it without a core, thats skill. he was able to
remotely absorb chakra from his trapped victims, something nagato wasnt capable of. the able were achieved after mere hours of unlocking the rinnegan, not even up to a day.
though nagato is the only one feat wise to have displayed basically all the paths but sasuke substitutes that for s/t, dimension portals and Rinnegan amped genjutsu, in addition to having the potential to display the rest of the paths. overall i say sasuke
