I'm not sure if anyone's ever actually reported diagnosed joint issues from Flying Saucer wheels - it's only been speculated at. I have yet to hear of anyone having a hedgehog have problems with it though.
I like cake cover wheels best. Bucket wheels are a close second, but cake cover wheels tend to be sturdier (with a rim that helps keep it from bowing with use) and bigger. But both are easy to clean, quiet, safe, and will last forever.

Bindi's cake cover wheel is from LarryT of Carolina Storm Hedgehogs (and Wheels), but I'm not sure if he has cake cover ones available these days or not. I know he was having problems finding the cake covers for a while. His bucket wheels are great too, my last hedgehog had one & loved it.