I always felt like they were sort of portrayed as very similar just Kaido looking a bit better. Things like their fight pre raid, people saying “it’s like fighting two Kaido’s!”, their sibling like relationship, their usage of elemental abilities, their backstories featuring them being basically offered up to the WG because of their combat strength and potential, both portrayed as people that are virtually unharmable through ordinary means, even their crews have such a similar feel. They’re such a duo in my mind it’s like thinking of Mihawk and Shanks, one is known as being the strongest but their rival is still very comparable/similar.