PieFed has more features and can do everything Lemmy can. There are many things you can do in Reddit but not on Lemmy, but most of those are possible on PieFed.

A user migrating to PieFed is more likely to stay than a user migrating to Lemmy, because they won’t have a feeling that there are familiar features lacking. You don’t have flairs, multireddits (a.k.a. feeds), polls, events, personal notes on users, or notifications on new posts/comments on Lemmy, but on PieFed you do.