Anson Williams started out as the co-lead, then was downgraded to third or fourth banana (depending on how you view Ralph Malph), and then found himself even further down the totem pole once Ron Howard and Don Most left (and Scott Baio and Erin Moran became the new young leads). By the end of the series, he was a complete non-entity and frequently the butt of everyone's jokes (remember Arnold's reaction when he returned to buy the restaurant and was wistfully commenting on all the new faces, and Potsie cheerfully announced that he was still around? "Why?"), and the fact that he didn't even make the finale speaks volumes. That, and the fact that he got beat up (offscreen) by Chachi during the last season. Think about that for a minute.
So I'd say that Potsie definitely suffered more than any other character. But Anson probably enjoyed cashing those checks regardless.