Naruto eats the Hana Hana Fruit and has gained enough experience to use it as well as Nico robin can, He has sage and fox techniques as well but his haki is about the same as niko robyns.(no crazy haki feats but still has his crazy ki.) VS
Luffy, who has through some reason or another gone and trained with the sage frogs in ninjustu and has learned the art of the sage(on par with naruto's) He is also post time skip.
Who wins? Neutral ground, on an island both know about ki and haki buff's. Luffy does not want to kings haki the guy.