Hey guys i'm new here but i'd like to put my 2 cents in here as well.
First of all are we talking about Sasuke would have fought against Pein instead of Naruto (Pein with gravitation abillities has no power till the end of the fight) or does he fight against Pein with all his abillities.
Well if it's the last, in my opinion Sasuke wouldn't stand a chance since he can't defend himself when Pein pulls him but neither would Naruto. As we saw Naruto was almost defeated after one pull. Of course Kishi didn't want him to be captured and setup the whole Kuubi thing and so on.
So if Sasuke fights against the weakend Pein it all comes down to the fact how fast his Susano arrows / amatersu is.
Moreover if Pein is able to dodge them or not. Sure one attack can be absorbed - but he's able to shoot more than one amaterasu at the same time.
It all depends on the fact if they're able to doge or not, since taijutsu won't work due to their visual link.
If genjutsu would effect all 6 path - I realy don't know. We just can assume that's not the fact, because than "the invincible Pein" would have a huge weak point.
He also has to deal with Pein + 4 Summons and has to take care that no one is resurrected.
So all in all in my opinion it's a 30% chance that Sasuke would win this fight.
But realy guys there are so many factors we don't know about the actual fight, like is he able to hit them? How long does it take to deafet them? Does Peins power return during the fight? And many others - that i think we can't say who would win.