Kakashi is such a good character. Your pic and sig constantly remind me of that fact.Minato obviously wins.
We have to be honest the rasengan won't do anything to Gay sensei's body. Minato will be taking a major L neg difficulty und he has around Kakashi level chakra reserves.In the end, all of Minato's jutsus are close range, both Rasengan and Hiraishin (as in, he teleports near the target to attack), which kinda boils down to a Taijutsu fight. Asuming Gai knows about Minato's jutsus due to history, If Minato wants to win this, he needs to get close against Gai, pretty much a death sentence.
Also, Madara fought them both, and even in that short skirmish, 7th Gate Gai fared better than Minato (senjutsu and all).
Chakra levels are not that relevant. Kisame had tailed-beasts levels and can be easily defeated by nins with far less chakra than him.We have to be honest the rasengan won't do anything to Gay sensei's body. Minato will be taking a major L neg difficulty und he has around Kakashi level chakra reserves.
Kisame was cheated but that's another issue, what I meant was that Minato wouldn't be able to fight a prolonged battle against Gay sensei.Chakra levels are not that relevant. Kisame had tailed-beasts levels and can be easily defeated by nins with far less chakra than him.
Don't know if "anything", but certainly Rasengan is not a one hit kill, specially to Guy.