I started on /kbin (MBin's predecessor) because I liked the UI and the philosophy. But then I wanted to host it myself and it being written in PHP I really didn't want to host it myself, I've been burned by PHP software too many times in the past.
Therefor I switched to Lemmy which was a nightmare to setup in the beginning because there was no documentation on how to do it. I still got it working after some time and was fairly happy with it. It was reasonably fast, the UI is good enough and it had a lot of 3rd party apps working with it so I could choose some other frontend on the phone for example. But over the last year every update made it more and more heavy to run as a single user instance. And then the current update made it so I couldn't run it on my small VPS anymore because it would create such a load that all the other services I'm running on it (Mastodon, some Websites, PeerTube, Matrix, etc.) would go down because of it.
So I switched to PieFed. So far it has been amazing for me. It's written in Python so it's super easy for me to understand and to fix things which I don't like. It has a simple theme engine which made it very easy for me to adapt a theme to how I want to have it. But the biggest advantage is that it's so easy on the resources, I can run it as a single user instance and it does not affect any of my other services running on the same server.
So there you have it, if you don't have too many resources available on your server I would go with PieFed. The developer is very approachable and aligns with my values more than the Lemmy devs.