Guess I think of the B side as a fighter who has no other way to make as much money as he would fighting a guy who does have other comparable options. Hagler-Leonard is a good example, Marvin was a dominant long time champion who had been active, but he was getting old and without any cash cows around, I don't there was any other way to make near half as much money as he did fighting Ray. Leonard on the other hand probably wouldn't have even taken the fight if he didn't get things his way. It's not always(if not even often!) a matter of who has earned what.