for me personally, i think sasuke would pwn narutos ass before the full transformation, (u now, with the eye and so forth cause the nine tails could be conrolled by any uchiha of the elite class, and sasuke, as we know - who defeated danzo, one of the three most powerfull ninjas in konoha- is of the elite class, and if not, more) naruto has proven himself, but still, in 571, they (naruto and the nine tails) indicate hat because it was their first time joining forces, they could only hold it for five minutes, so if naruto would have to beat sasuke up, he would have to go full power as soon as he could before he loses his power.
what do you think??
what do you think??