I think the point here has nothing to do with statements of the characters at one point in the progress of the manga. Naruto and Sasuke were rival and needed to be matched at a certain instant, but it was really clear that they would be very different afterwards.
1. Different goals means different power
Sasuke and Naruto always had different goals.
Naruto wanted power to be acknowledged by everyone in Konoha. This includes Sasuke as well, and it meant to become the greatest ninja of Konoha - the Hokage - which also mean to place his life on the line for the villagers. Not only that, but he also planned to surpass all the previous Hokages.
As you can see, Naruto's goal make him the strongest ninja of Konoha, including being stronger than Sasuke.
On the other side, Sasuke's goal was to beat a single person - Itachi . His quest for power was to surpass Itachi, and he had to leave the village for that. After beating Itachi (better after being saved by Itachi from Oro), Sasuke's goal was over. In order to please the fans, Kishi gave him a new goal, but even with that, it is easy to see that Kishi cannot overdo it lest he ruin the manga. This is why all the theories concerning Sasuke have failed lately. He got no power from the scroll, got no fight with the Hokages, etc. I know he has a new power, but he will be a mere tool to support Naruto.
2. Naruto acknowledged by everyone including the previous Hokages and Sasuke.
The manga is all about Naruto. A kid whose gift was hidden initially and shadowed by the Kyuubi and his being rejected. Everyone including his friends treated him as a failure while he himself considered has the greatest and smartest ninja that will ever exist.
My interpretation of the setting is that Kishi is putting all the pieces together for Naruto crowning. Sasuke, the Hokages, Oro, and even Madara will all be moved when unexpectedly, Naruto will defeat the Juubi. My opinion is that Sasuke will use all his weapon, yet still fai. Everyone will use their power, then fail. After everyone is down, there will be one man standing - Naruto. It will look like Goku vs Majun Bu while Vegeta finally admit that Goku is in another level of power.
Look at the similarity:
- Super Sayans -- Ancestor of both Goku and Vegeta: Normally, according to vegeta, he is the prince who should be super Sayan easily, but strangely, Goku becomes the supersayan first and keep mutating easily. Vegeta had to resort to uncommon method to become Super Sayan. But at the end, he never reached Goku's level. Here Goku is replaced by Naruto, and Vegeta by Sasuke.
- Majun Bu and the kind of priest who defeated him: There was Majun Bu (here Juubi) and a guys who sealed him (here Rikudo). Then someone used Sayan's energy to free Majun Bu ( Sayan energy - Biju energy). I am pretty sure the priest represents Rikudo and Sayans are actually the rare Uzumaki who can become Jinchuriki of Kyuubi or Juubi just like Rikudo.
Well, I think the two series are identical. At the end, there will be a good Juubi maybe helping Naruto to defeat the bad one (or whose power will be used by Naruto).
If we go by that, possible twist:
- Vegeta gave his body to the mastermind so that Bu can be complete with a promise to control Bu's power. But afterwards, vegeta's pride turn him against the mastermind and end up dead. It is possible that Sasuke give his body to Madara with an expectation to overtake his power - but fail.
3. Naruto has always be more powerful than Sasuke
It is clear for me, Naruto has always been more powerful than Sasuke. It is the same as HAshirama and Madara where one think of creating peace while the other is bent on his own self. Consequently, the other is giving his all out during a fight while the peacemaker is thinking of a way to convinced him.
This alone show how the task of the peacemaker is difficult. At the end, we saw that Hashi was at god level while madara was living in an illusion.
