They each are good in different ways. Lemmy's search is superb - far better than Reddit's or especially PieFed's. Though PieFed has solved the community discovery and onboarding issues for new users.
Imho PieFed seems unquestionably better for a new user, whereas Lemmy is typically more suited for an established user of the Threadiverse, unless they want one of the new features that only PieFed offers (i.e., most people don't need to move, especially if they use a mobile app).