• Communities can have a topic, this means you can browse by topic! Nice but not mindblowing
• Communities can define post flairs! Basically very visible tags on posts that you can sort by. I’ve wanted this for a long time and some communities do this on lemmy by adding [flair/tag] to the title. Easy to forget to do. With it being a feature instead it’s just much nicer and handier
• Wikis! Some communities really benefit from having a wiki alongside it, like my DIY HRT community! I’m super pumped for this one
• There’s a NSFL flag for posts in addition to NSFW
• Lots of neat options for communities and the user. You can set communities to be mosaic instead of a list! Haven’t tried it yet but it’s cool that it’s an option
• Built in custom css stuff
• The dev seems very active and communicative
• The dev isn’t a transphobic tankie as far as I’m aware
• Everything seems to be better made than here. Did you know on lemmy you need to comment/post in a community to be made a mod? You also can’t be unmodded unless you have a comment or post. On piefed there’s a menu for this instead. Lots of just better little things like that
• More probably

The downside is Lemmy is more popular. I don’t think there is a mobile app also (edit: there are mobile apps like Interstellar, but I dunno if they support all the non-lemmy features yet), just the web frontend. There might be more, but I just started using it. Also, since the instance is new it’s still syncing posts and such from other instances and from lemmy

Edit:
Oh! And you can have “feeds” which are like multireddits. Instead of just your frontpage which acts as a singular feed you can have multiple custom feeds! Say a meme and a hobby feed f.ex, instead of everything being mixed

Edit:
One more negative is lemmy can’t see the piefed only features like wikis. It’s also newer and there seems to be mainly one contributor to the code, so I wouldn’t be surprised if there are some bugs lurking around.