I don’t know much about Gacy, but I think he killed more people. However, by the time he was arrested, Dahmer was killing once a week. And he ate and dismembered people. And fucked their corpses.
I’d really think hen it comes to them, there’s probably not an objective measure. However, Gary killed less frequently; he just got away with it longer. Only thing I know about him is that he was a pedo who dressed as a clown.
And they were both gay. (No offense to gay people. Just saying thats a partial motive for them.)