I don't think the portrayal were the same. This is how Oda portrayed Oden vs Kaido
10 vs an army
	
	
		
		
	
	
Long battle where Oden despite being vastly outnumbered with Kaido taking advantage of the chaos to spread fire in Oden's direction, with Oden's endurance far exceeding his expectations, Oden still manages to almost kill Kaido, with Kaido at Oden's mercy before the kidnapping shenanigan
	
	
		
		
	
	
With Kaido's final hit happening when Oden was 
distracted after a 
long battle of endurance.
Luffy on the other hand was alone against Kaido, and not only failed to damage Kaido, but got one shotted
With that said, current Luffy should be able to damage Kaido with advanced hardening, so i'd not be surprised if they currently were on the same level. Let's see how it'd go though