Kbin also has Mastodon integration (though it's still being worked on and isn't in its final form yet), which I think is handy because I'm hoping that Kbin doesn't defederate from Meta, so that I can also still have an account to keep in touch with people I care about who are going to be using Threads without having to manage another account elsewhere.
I also prefer the layout to Kbin better. While the stock Lemmy layout is nice (it does a fantastic job of emulating the old.reddit layout), I like the fact that Kbin shows a little bit more text about each post. It also keeps more data public (like your votes and reputation scores), which I actually prefer being out in the open, as it helps weed out people who may be giving bad faith arguments in various discussions.