Titles aside, we can just look at how the most known pirates perceive Whitebeard comparatively to Kaido
- Big Mom is someone who has known Kaido for decades, thinking of him as her little brother, but she seperates Whitebeard from them
"even Whitebeard"
- Doflamingo is someone who has been Kaido's business partner, with his nickname(Joker) being a left-over from the beast pirates hierarchy, actually know Kaido's strength enough to be scared just at the prospect of facing an angry version of him, but he knows that Whitebeard was sitting infront of the throne
- Garp is heavily knowledgeable about the Rocks pirates, but he knew that Whitebeard was the king of seas
- Whitebeard was the benchmark to Teach(potential final villain) like Roger is to Luffy, the equal of even the pirate king, the final benchmark of the manga