A comment I came across like two weeks ago puts it quite well:
I haven't used piefed myself but I wouldn't want to switch to it because I feel like it gives more power to downvotes and karma (or "reputation" as they call it):
- Comments with -10 score are collapsed by default.
- People who get downvoted a lot end up with a ‘low reputation’ indicator next to their name. You’ll know it when you see it.
- Upvotes in meme communities do not add to reputation.
Those are three of the twelve points listed as differences to lemmy on their features page.
I also don't agree with some of the points in their article on "PieFed features for growing healthy communities".
from: https://sopuli.xyz/comment/17119490
the comments' thread is also quite interesting
Plus it's written in Python and has only a few hundred MAUs, so we can only guess how well it scales
EDIT: Regarding Lemmy frontends, I suggest you take a look at how the instance I'm on handles it. They append a single char in front of the url to signify the various frontends