User blog comment:Staw-Hat Luffy/Why Kaido?/@comment-5896530-20130204100151/@comment-4605926-20130205140936

Well, it was clearly stated in the last last chapter (aka 697) that Kaido is said to be the strongest creature in the world. While one could argue about the term "creature", I believe this is enough to conclude that he is currently the strongest being in the world (since Whitebeard died). However, this does not necessarily mean that Big Mom's crew is weaker even if the captain is stronger. A crew's strength is not measured by its captain's might on his own but by the strength of the crew as a whole. Also, nobodoy ever said that Kaido was significantly stronger than Big Mom, just stronger (which again does not say anything about the crew as a whole). I think it's fairly obvious that there would be certain differences in terms of strength between the Yonkos and their respective crews, that's just logical.