We'll just have to wait and see, there is so much more to be explained about the SO6P and the Jiubi...Like why did the Jiuby had that 9 tomoe rinnegan, what abilities did it have, how did it gain that eye if the sage only had the rinnegan?
Who Knows... maybe in the end Sasuke ends up with that freaky eye, which would mean Naruto must have the Sage's body... like complete.
anyway in the end, the deciding factor will be the ninja way of each of them, who's will is stronger and who has more reasons and faith... The amount of power will be equal, or at leas i hope so, otherwise it would be weird to see a fight in which one of them is extremely op and just rapes the other.