1. sasuke has not always been better than naruto, which is one of the reasons sasuke strived power from orochimaru,
2. valley of the end was in the past, this is now.
3. when they first meet in shippuden was in the past, this is now.
4. Naruto admits that he doesn't think he could be sasuke, but madara tells sasuke that naruto would beat him, and i reckon madara is right. Also that was in the past this is now.
5. naruto has now achieved nine tails chakra mode, is close to perfecting the tailed beast rasengan, is the fastest person alive and also has sage mode in which he can enter in a few moments of stillness. Sasuke has gained EMS which we don't actually know if it will grant him new powers or if it just stops him from going blind, personally i think he will unlock new powers, but naruto will still be able to beat him, not to mention naruto has more powerful summons, could probably combine ninetails mode and sage mode and has the power itachi gave him.