Ok i get that, but the reason why people say that is because King was able to easily handle an attack that cut Kaido and made him feel pain.
I put King over Kaido because of his defence and durability but i dont think he can endure as much as Kaido, seeing as Kaido has taken a shit load of attacks, i dont see King being able to take as much punishment as Kaido, but the fact is King can counter those attacks because of his special ability, so its not right to disregard his power for the sake of Kaido > King which should be obvious