Considering Luffy got a recharge via food and Kaido took on a gauntlet, got scarred, and didn't rest once, it's not even up for debate who's stronger between kaido and Luffy lmao.
Speed
Physical power boosted by speed.
Lasers which ignores durability
Kizaru is a unique adversary unlike brute force fighters.
Sure, if you just ignore all the damage Luffy went through and the fact he was practically dead before Gear 5 brought him back. 1045 showed him to be clearly exhausted, even Kaido warned him that he could die if he kept going, Kaido landed way more hits than Luffy did in the final phase, and Luffy still had enough left in the tank to win a direct clash of sheer strength to win the fight overall. It absolutely is up for debate when Oda creates the narrative of Luffy surpassing Kaido and Big Mom in Wano itself ("I will surpass you" x2) and Kaido himself then saying that Joyboy is the man who can beat him. Not to mention Oda giving every power-up possible to Luffy in one arc, Kaido getting a sake break after fighting the Scabbards etc.
But anyway going back to Kizaru, the pre-TS Supernovas were able to take his kicks and even Luffy in Marineford - heavily affected by exhaustion and the treatment he got in Impel Down - was able to take one of his kicks back then without being knocked out too. Kizaru has not done a single thing since then to convince me that he could push Luffy to high/extreme-diff, much less stand any chance of beating him. The only reason why I think it should be high-diff anyway is because I don't want the Marines to look any more embarrassing than they have as of late.
I think this arc will show that he won't be able to pull up on the Straw Hats like he did in pre-timeskip, I personally don't powerscale using a character's confidence. We saw how well that went with Ryokugyu.