First, please calm down... now that you're calm +rep... Thanks
Now it is readily apparent to any attentive reader that Naruto and Sasuke are not at equal power continuously, i.e. at every single point in time, throughout the manga and to claim so to claim so such a specious argument that it's actually quite shocking to read it.
Kishi was referring to Sasuke and Naruto on a larger more thematic scale when stating that they're always equals. On a smaller and more discrete time scale, Sasuke and Naruto do not stay equal and there are fluctuations in who is stronger, which has been evident in the manga since before the time-skip going back to their days at the academy and their first mission. Even on the finest scale one can point to their competition of tree walking task, lol, but that time bin is so small it's impractical for most things.
Sasuke initially surpassed Naruto via his natural genius and training, until Naruto's use of the Kyuubi (ex. Haku, but that was unconsciously done due to his emotion at thinking Haku killed Sasuke) and his training with Jiraiya to willfully unlock the Kyuubi. This was quite evident in the Gaara fight if you compare their respective performances and left Sasuke speechless after Naruto did 2,000 clones, summoned Gamabunta, and saved Sakura (granted Sasuke used up some of his chakra on Chuunin exam on Gaara, but so did Gaara. Further Sasuke admitted to Sakura that Naruto saved her, not him).
In fact, Sasuke and Naruto fuel each other, Naruto fuels Sasuke by wanting to be equal to Sasuke and gain his recognition, and Sasuke is fueled by being infuriated by a "failure" such as Naruto considering himself an equal to an elite such as Sasuke because if such a "failure" is his equal how can he accomplish his goals?
This is a theme that dates back to the beginning of the manga and is one of the major reasons Sasuke left the village to seek out power. An excellent example is when it boiled over on top of the hospital:
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This is their first showdown of Rasengan vs. Chidori:
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Sasuke's reaction to seeing Rasengan's true destructive power:
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Then you look at their battle at the Valley of the End. Naruto pulls out a little Kyuubi chakra and Sasuke's 2-tomoe Sharingan can't keep up with the speed of Naruto's taijutsu, so he awakens a full 3-tomoe Sharingan and all of a sudden can keep up. Next up, Naruto goes 1-tail Kyuubi cloak, again Sasuke has issues and is eventually forced to go CS2, which he just received but never activated. They end in a draw with Sasuke going for a fatal blow using Chidori and Naruto simply trying to scratch Sasuke's forehead protector with Rasengan. Sasuke wakes up first, and leaves for Orochimaru seeking out the power another way than killing a sleeping Naruto, a corollary to what his brother insisted was necessary for the MS...
At the beginning after the time-skip, Naruto is admittedly in his base-form not the equal of Sasuke's base-form during their reunion, granted he was weakened from being in the 4-tail fox cloak and fight with Orochimaru.
This is verified by both Kakashi and Jiraiya. Kakashi sees the upside of this as that Naruto will be inspired to train for FRS. How does Sasuke stand against 4-tails Naruto at that stage? Speculation, so please don't say they're equals. I honestly don't know if Sasuke could've survived against a 4-tails Naruto, but I'm not going to claim 4-tails Naruto the winner either because it's speculation.
After defeating Nagato* (*yes I know he received help (Kurama and Minato), intel via Katsuyu, and plot no jutsu)
Zetsu states that sage mode Naruto is probably more powerful than Sasuke to Sasuke and Tobi before Sasuke heads off to the Kage Summit with his MS:
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How much of Zetsu's statement was being an honest assessment from his perspective of all the fights he's recorded and how much of it was being taunting...? I can't be 100% certain, but Zetsu hasn't been the taunting type that much in the manga in comparison to say someone like Kisame, who is the exact opposite and then the comment would have to be taken with context of the character. As well, Zetsu did not correct himself, which seems to indicate both white/black Zetsu agreed, which could be viewed as two independent sources, given that during the 4th Great Ninja War they've been separated for the majority and thus seem capable of existing apart as well as conversing and disagreeing with each other (examples include disagreeing over whether to watch the Nagato or Itachi fight, which of course occurred sequentially. Conversations during the Itachi fight are plentiful where one Zetsu has knowledge the other doesn't.)
It's not terribly surprising either if Zetsu was correct given what Sasuke displayed with his MS up to that point against Bee, and given that he hadn't awoken Susanoo to our knowledge until his fight against the Raikage. This is especially likely since against the Raikage he awoke the Susanoo initially only as the ribs, and awoke it substantially more as time surpassed but had to augment it with Enton (blaze release, Ameratsu controlled) to shield himself from the Raikage.
This is really an excellent example of Naruto and Sasuke being around the same power level, yet unequal, but at slightly different times, especially since we have the manga stating it here via Zetsu along with our own ability of insight along with a history and future of writing from Kishi. A Sasuke with a MS that has poor Tsukiyomi (i.e. no time control), Ameratsu that did not have Enton/blaze release (just an on/off switch), no Susanoo, Kirin (under the right conditions), and failed to capture Killer Bee compared to a Naruto with a perfected sage mode, FRS, and his powerful toad summons that just took down arguably the strongest member or one of the strongest members of Akatsuki (Itachi, ...) probably could be called weaker.
Particularly considering that Zetsu, unlike Tobi, didn't even account for the possibility of Nagato failing:
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Honestly, this last point should drive it home pretty loud and clear. If you think about this logically, which I hope that you're still with me, despite the length of the post. The manga is published once a week, OK. There are approximately 48 issues a year; thus, we can bin a year into 48 bins if we want to. For latter 2011 and 2012, how many bins has Sasuke been sitting in a cave doing nothing? I don't know off the top of my head but, we can say for all but a few, Sasuke has been in a cave with his eyes covered in bandages. During that same time period, shadow clones of Naruto in Kyuubi mode (KM) and sage mode (SM) each week/bin have been taking out ET Kage's, white Zetsu's, and powerful opponents such as recently Tobi's six paths of Pain. As well, recently he gained Bijou mode:
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Where was Sasuke, and what was he doing? The most incredible thing we've seen Sasuke do is torch some White Zetsu's, which are cannon fodder, with Ameratsu, and interrogate one with Tsukiyomi, albeit his chakra efficiency looks better. You're advocating that they were equal this whole time. That's absurd. By what metric are you measuring them?
They fluctuate in power constantly due these power ups and the discrete nature of the publishing of the manga. The only time they're actually on the approximate same level is when the actually battle each other, and even then there can be fluctuations as seen in the pre-time-skip battle at the Valley of the End, albeit I don't think that will happen again to Naruto, not sure with Sasuke.
Look at the period you average over, is it over a month, well Naruto is still more powerful than Sasuke has demonstrated at times, and vice versa, again based on power ups and the discrete nature of the publication of the manga, which tends to focus on one of them at a time unless they're fighting one another.
It's a totally contrived and naive notion that they must be constantly equal in power to be equal when they fight, as all that matters is what happens when they battle. Honestly, we don't know enough about the EMS to even know Sasuke's limits, and Naruto hasn't even perfected BM to know it's limits either. Historically, however, they're never equal in power unless they're fighting each other, and they're equal in power only transiently.
In fact I'd say they spend much less time equal in power than they do slightly unequal in power due to fluctuations.
Peace