And Warlord definitely is a level, people use the term all the time. There are weak Warlords and strong Warlords, just as their are weak Marines and strong Marines. And I never said being admiral level makes you equal. It's evident they aren't equal if one can beat the other.
They use the term, because they are famous and that's their title, just like Luffy is captain, but as I explained captain is not level of power. Mihawk was able to fight with Shanks for many years, which would make him close to his power, or even equal. Latter is Yonko. Buggy is so weak that he lost to Luffy in East Blue saga. Which would make great difference between strongest of Shichibukai and weakest of Shichibukai. Also, in order to be Shichibukai, you don't need certain power level (like you need in order to be Yonko or Admiral) again example of that is Buggy.
Then why did you say they are both admirals, when
Aqeel96 said difference between them are very small.