1.) Their fight on top of the hospital. The damage to the water tower was much larger from Naruto's rasengan than Sasuke's chidori.
2.) Sasuke and Naruto colliding at the bridge after Danzo battle. Sasuke was knocked way further back.
3.) VOTE2 Sasuke has to use Amaterasu enhanced chidori just to match standard rasengan.
If you're gonna pick at the word "overpower" then lets just use manga facts to say rasengan is stronger, which is obvious. Agreed?
1) I agree but keep in mind chidori is more of a frontal attack as while sasuke did more damage in the front, naruto's rasengan did more damage to the back and this was before Sasuke got some grip on his curse seal.
2) maybe because Naruto cane in full health, and sasuke was bloody beaten from his fight with danzo, and he still managed to fend kakashi off in a taijutsu battle and the spamming of Susano left sasuke extremely weakened in comparison to Naruto? The fact that he could clad at all without getting his chidori broken says a lot.
3) wasn't his eye powers weakened according to kurama and also chidori is weak against wind release:rasengan, because wind>lightning, but fire is stronger than wind which is why he used Ameterasu to compensate also naruto's rasengan was also kurama enhanced, why do people keep forgetting kurama gave Naruto the last of his Chakra making his rasengan enhanced as well.........
By definition rasengan is supposed to be stronger than chidori as chidori is a weaker version of rasengan with just enhanced shape formation from kakashi's failed attempt to copy rasengan and chidori in essence is supposed to be weaker than raikiri, the fact that Sasuke could use such a jutsu and still match with supposed stronger ninjutsu says a lot.