The difference is, you expect Luffy to beat Kaido in a one vs one. I cant imagine that too for now. I would expect a Tag-Team-Fight together with Kid against Kaido. He main solo fight against a Yonko will be Big Mum, after Wano. Thats how i imagine the going ups.
Also Kaido does make a huge mistake here. He neg diffed luffy for sure, but he did while Luffy was furious, out of concentration, unfocused and unprepared. Luffy didnt know with what Kind of force, what Kind of strength he has to deal with. But now he knows, now he is prepared, now hat trained explicit for Fighting Kaido. Something Kaido doesnt take into his countings. Again, why should he. He thought he is in Udon, was broken down. Yeah he escaped kinda, but how should he have trained? Kaido cant assume that too.
In a fight against Kaido, Luffy will be way more calmed, way more focused, concentrated and knowing how to fight him. He will be able to use his Haki, all 3 of them, he will take care of attacks, of dodging, of hitting specific Points. Something he absolutely didnt at the first "fight".