Before final fight with Sasuke, Naruto had half of Kurama (Yin). The two friends were equally powerful.
After the fight, Naruto received the other half (Yang), as given in manga.
Does this mean Naruto's powers doubled, making him stronger than Sasuke?
Not necessarily. We could say that this does increase Naruto's powers drastically in comparison to Sasuke, but there are a few things to consider:
The important thing here is that by getting the other half of Kurama, Kurama doesn't necessarily become a stronger tailed beast, he merely gains more chakra. This is, of course, very drastic, but it does not allow Naruto to fight any better with Kurama. He can still use the same abilities, and infuse the same amount of chakra into them, he just has more stamina now.
Naruto is an Uzumaki, which is a clan famous for their large chakra reserves. On top of that, Naruto already had the first half of Kurama which gives him an overwhelmingly large amount of chakra right off the bat. The addition of the second half of Kurama will increase by a lot, but not in comparison anymore. It's like trying to make an already blue flame even hotter. Maybe you can, but by comparison, the difference is minute since it was already so hot to begin with.
This is pretty simple. Naruto's power never came fully from Kurama to begin with. While we could say a good deal does, he still had and has various other abilities that make him an extremely strong shinobi.
In fact, Naruto was being severely hindered by two things. The first being that he had been fighting in this war for much longer than Sasuke, and was much more tired out. The second thing is that Naruto was unwilling to fight to his fullest (especially in the beginning) for fear of killing Sasuke, whereas Sasuke did not hold back. So even if the second half of Kurama did make Naruto twice as strong as before, it would not make him exactly twice as strong as Sasuke as they were never on equal ground to begin with.
The simple answer to this is we don't and can't know. We can merely speculate. As we see in the Scarlet Spring, we know that Naruto's combat instincts have dulled whereas Sasuke's could have only sharpened. This means that the two have probably leveled out
