It's come leaps and bounds since it launched--I've been stalking the GitHub and the current dev build is nice. The App Store version is still a little rough but they've got an update in beta that smooths it out a lot
Memmy is the best I have found. A lot of the issues recently have been related to instance problems like with lemmy.world. Stuff that Memmy isn’t at fault for.
That said, I am very excited to try the Voyager iOS App when it releases!
Liftoff has been super stable all the time I've used it, Infinity for Lemmy is surprisingly stable for something new, I've had no crashes at all. Both of them are updating very quickly and get better all the time.