Im not talking about part1 , im talking overall about the series. Naruto was using Kuramas chakra even when he didnt control it/ vs Neji for example - and what action ? He had screen time, thats why the action was needed. And what training was he doing exactly? When he was learning SM - he was just learning how to control SM chakra with the help of the toad again. Sasuke was doing real training and never had to rely on side power ups such as SM and other stuff - MS /EMS just ruined his fighting style anyways - Sasuke would alrdy get the Rinnegan same way MAdara did with senju dna - Hagoromo only (powered up the process/speed) of getting Rinnegan which was even nerfed so Naruto could actually stand a chance. If you dont believe me, check EDO Nagato vs Kurama Mode Naruto, Naruto could even touch Nagato.
Madara was alrdy weaken from fighting 8gates Gai and Naruto just came to show up just in time to throw that Rasenshuriken - Sasuke actually Blitzed Madara