The logic im using is that Sasuke traveled the world. During that time he would have mastered the rinnegan while also improving his other abilities. On the other hand, Naruto stayed in the village so he barely fought, except for training, with anyone.( Most likely) And Naruto didnt have anything else to master, except shunshin(which he did), while Sasuke still had so much to master with his rinnegan. Hell, he might have learned all the chakra elements.
So, Sasuke in its path to reunite with the world and all the pacifist crap, just went on and battled everyone gaining exp to master his rinnegan?
Oh, and Naruto had lots of techs to master:
-All natures he gained trought the infusion of the bijuus chackras (that's a lot of Rasengans to master, although we already got a show of it)
-A bazillion kinjutsus, that as an Hokage he has access to;
-Lots other jutsus from fuinjutsus;
-Creating more jutsus (Naruto excells at this part)
Bottom line, Naruto's abilitties are much more raw than Sasuke's, but that doesn't equal to Naruto mastering those, it's just potentially he has much more to train then sasuke. At the peak of their capacities, Naruto is far stronger than Sasuke (and that's just an opinion now, but, as in the 1st part, Sasuke just uses its abilities to a greater extent (like 95~99%) while Naruto, just uses them at lower (70~80%)
