They're both equal as of now. Naruto's access to Kuruma's chakra could be limited if Sasuke drops by. Considering he managed to suppress some of it's chakra at the start of the timeskip, who knows how much he can do now? Naruto still has the advantage though...
People presume that Naruto wasn't going flat out in The Valley of The End but he must of been, the desperation that he had drove him right to max. There's a pretty obvious reason he didn't use a summon. Because it would've been Gamabunta, which is ridiculous against one 13 year old kid. And of course this is the first time Naruto has properly gone Version 1, you can't expect him to be able to handle that much power in it's first instance...
Anyway, yeah they're relatively equal with a tad more to Naruto. Whatever powerup Sasuke gets will fully balance the playing field.