I just want to a say a few things...
1. I agree & disagree that Sasuke is smarter than Naruto. Sasuke shows tremendous ability to plan in preparation for a battle(Itachi & Orochimaru for example), but Naruto has shown tremendous ability to think quickly on his feet(Neiji & Pain are examples). Even in their own fight, they were dead even.
2. I agree & disagree that Sasuke is faster than Naruto. Sasuke was traditionally faster than Naruto, but his time with Jiraiya changed him. He has already been shown to have a base speed comparable to Sasuke. Sage Mode increases that and so does Fox mode--a combination of the two would be insane. That said, Sasuke has ALWAYS trained on increasing his speed since his days with Kakashi--hence, Naruto thought Sasuke was beyond him in speed when they met at Orochimaru's old hideout(Naruto WAS exhausted and still healing though).
3. Susanoo is great, but a tremendous drain on chakra(from what was said). Unless Naruto was forced to try and end the fight quickly, he can wait out Sasuke as he has BOTH Sage mode and Fox mode at his disposal--not to mention a higher chakra reserve.
4. Their rivalry pushed them to new levels before--I have no doubt that another fight between them will do the same again. They bring out the most out of each other.
5. Naruto is not the same little kid he was before. The Pain saga shows just how much Naruto has grown. I doubt Naruto would hesitate move to take out Sasuke if that was what was required. Naruto understands the bigger picture probably more than anyone else in the Hidden Village(again, thanks to Jiraiya).
6. Naruto will probably SOMEHOW lose the Fox powers(probably to Madara) and will team up with Sasuke(maybe).
7. I want to believe Sasuke still has some goodness in him, but that has since gone out the window. Yes, Sasuke did annoy Orochimaru by not killing anyone earlier, but he left two of his teammates to their fates, mortally wounded Karin and attempted to kill Sakura.
Just my two sense on a few things. Keep in mind, I am NOT a Sasuke fan. I am one of the first people to complain about his little emo whining. Taking a step back and looking at the bigger picture though--this is what I see.