Which later season era of two of Garry Marshall's 1950s set sitcoms was better? The post-Milwaukee seasons of Laverne & Shirley in Burbank, California (Season 6-8) or the post-Richie Cunningham seasons of Happy Days following Ron Howard's departure at the end of Season 7 (so Seasons 8-11) in 1980.

Laverne and Shirley I think!

Happy Days. I still like the post Ron Howard seasons, they aren't dreadful like so many think. Henry Winkler, Marion Ross, and Tom Bosley were in the whole series, and Erin Moran was in all but season 10. I haven't seen California seasons of Laverne and Shirley but it should have ended after season 7, would be pointless without half of the title women.

Laverne & Shirley seasons 6, 7 & 8

Wow, this is really tough. The last season of Laverne and Shirley had some of the worst episodes in sitcom history like the one where the apartment was haunted and without Laverne there the ghost makes the cast go through an obstacle course.
Having said that, Happy Days jumped the shark even before Richie left but he left it became the Fonzie show even more.
I would have to flip a coin but I would probably still think Laverne and Shirley was better.