Sasuke's Indra arrow against Naruto's rasenshuriken were meant to stand for more than simply two strong attacks. They represented the uniqueness of the two characters, and was the culmination of both of their paths in life, so from the beginning more than anything else they were meant to cancel each other out completely. This is from both a narrative perspective and in-universe perspective, so keeping this in mind let us consider the attacks.
Sasuke, and the line of Indra transmigrants before him, represented power. However, there is an underlying meaning in the Japanese that may not be readily understood, and that is not power for power's sake, but the ability to dominate through power. The leader of ninshuu meant being in a position over others, controlling them (Hagoromo controlled, and had to decide on an heir to CONTROL) and Indra decided that the way he wants to CONTROL is through POWER. With that said, Sasuke using the bijuu chakra was different than Naruto using it because, though he used their power, it was done through him dominating them. He combined this power with his personal avatar of power, Susanoo. Sasuke's susanoo is the only one shown to have a bow, a unique trait to him alone. The significance of this means that Sasuke's strongest attacks are piercing powers (chidori, chidori eisou, susanoo arrow, etc.) and that combined the bijuu makes it one of the two strongest attacks available to anyone post Kaguya's defeat. Sasuke is the bow that guides (controls) the arrow which are the bijuu.
Naruto on the other hand represents domination through love. The ultimate showing of love is cooperation, and this applies to any interpretation of the word in any language. Naruto cooperates with his clones, He cooperates with the bijuu, and very significantly he cooperates with nature (sennin mode.) Using beast chakra, natural chakra, and his own chakra in the form of clones, he created the ONLY attack he has that is unique to him: rasenshuriken. I say this because no one else can use this technique, and is more of a representation of Naruto's ideal than just the rasengan. He also created two, just to show that even his attacks will be cooperating with each other to go against Sasuke's one arrow.
In short, the attacks are perfectly balanced because the characters using them are meant to be perfectly balanced. Balance also does not have to mean being of equal strength. Sasuke should be, for all intents and purposes, more powerful than Naruto. He has the rinnegan and all of the abilities that come with it. However, he only has one arm, so he cannot utilize hand seals. He has ocular jutsu to subjugate bijuu and human alike, but his friendship with Naruto keeps him from doing wrong anymore.
I hope that this was not too confusing.
