I'll answer this objectively
here is a list of sasuke's improvements: in part one, his skills improved marginally but his only noteworthy boosts were 1)Sharingan activation, 2)two-tomoe sharingan activation, 3) Curse mark 4) Speed boost during chunin exams/ learning chidori, 5) 3 tomoe sharingan 6) CS2 activation.
naruto's part one improvements are as follows: Firstly he started MUCH lower in skill than sasuke. his first giant improvement was the use of the multi shadow clone jutsu. Some people disagree, but i think this brought him instantly to be able to fight with sasuke (remember him tying up sasuke in episode 3). He then improved a bit by learning to walk up trees. As we saw, him and sasuke were equally as proficient at that. Naruto's next big power was entering the initial jinchuriki state (the form he took against haku, and then again against orochimaru in the forest). naruto didn't have a giant raise in power until he had his five pronged seal removed and learned to walk on water proficiently. Then he learned to control some of his chakra and use the summoning jutsu. Honestly, at this point, naruto would destroy sasuke (as we saw how much better naruto fared against gaara than sasuke). Then naruto learned the rasengan. His final upgrade was awakening the 1 tailed shroud in the battle against sasuke in CS2. In that form, naruto and sasuke are around equals, but if you take away those, naruto should have dominated sasuke with gamabunta. So in part one, naruto increased the most.
Time skip:
In the time skip, sasuke clearly increased more. he used drugs etc to increase his physical ability and skillset substantially. naruto too grew some, but not to the same degree. It is at this point that sasuke learned kirin and all of his chidori variants. he also was capable of performing the summoning. However if you're taking into account them in powered up states: naruto grew the most. Sasuke's CS2 state didn't noticeably change, but naruto was able to go into the 3 and 4 tails cloak (although not at will).
Sasuke doesn't receive a power up again until sasuke learned to use the mangekyou sharingan (and lost his curse mark). Naruto around the same time completed the futon rasenshuriken, and achieved perfect sage mode. in my opinion, this is naruto's greatest accomplishment. All of naruto's shortcomings stem from poor skill level and low maturity. Achieving this form made him top tier in basic ninja arts, but also have potentially limitless chakra. He also made it all the way to 6th, and then 8th tails form. Naruto at this point is stronger than sasuke (as admitted by black/white zetsu who is known specifically for being able to tell a person's capabilities). Sasuke's next powerup is his ability to use susano'o, but it greatly weakens him. naruto learns to master the kyubi's chakra and becomes almost unstoppable. He's the fastest ninja in the world, and has chakra exceeding nagato's own in volume.
Naruto again gets a huge boost by achieving bijuu mode form. In this form, he is able to turn into kurama and share copious amounts of chakra with anyone he wants. He also has the bijuu bomb in his arsenal now, and even greater speed.
Sasuke achieves ems, which as of yet has only showed him able to use ms techniques without becoming heavily fatigued. He also has legs on his susano'o now.
Naruto then mixes his sage mode with his kyubi mode and becomes bijuu sage mode. In this form, he can actually use sage jutsu techniues on a kurama level (such as sage mode tbb and kurama rasengan).
Naruto is clearly the one who's grown the most
