Yin and Yang need to be balanced in order to mix. Sasuke = Naruto + 9 Bijuu
Sasuke + Hagoromo's Yin power=Naruto + Hagoromo's Yang power.
The bijous are part of Naruto's heritage and yang power (together with an empowered version of senjutsu, the sage's senjutsu), just as Sasuke's left eye and sharingan, are part of his heritage and yin power. His susanoo is empowered since he gained the sage's power too.
Sasuke had Itachi's sharingan implanted and he wasnt born with it (he would be blind without it).
Naruto was already affected by the bijou Kurama, while in the womb of Kushina, but lets say he wasnt born with it.
Both were meant to gain this. Naruto the bijou friendschip + cooperation and Sasuke Itachi's eyes. Naruto had to befriend the bijou, something that previous jincs hadnt done and thus had not succeeded in. Sasuke had to learn how to handle Itachi's eyes. Naruto had to learn senjutsu (having Kurama inside of him at that time only made it more difficult).
So far in the Kaguya fight, from observation one would say Naruto>Sasuke.
However Sasuke has been brought back by Sakura and Obito and his left eye will come off cooldown.
So I believe Kishi will make Sasuke shine a bit more soon so that we can conclude Naruto=Sasuke.
Basically you cant remove bijou's from Naruto and than say hey Sasuke is stronger.
You would need to remove for example the left eye from Sasuke in that case.
