Do you have any proof they're equal? Wano Franky is as strong as Punk Hazard Franky who's weaker than Vergo. Franky lost his armor. Had the fight continued, Franky lost. Jinbei would beat Who's Who again if Who's Who got up again.
Rival doesn't mean equal strength. Bege and Luffy are rivals for example. Shanks and Buggy have been paired together