This site might help a lot with finding the equivalent subreddits on Lemmy and Kbin. It even tells you which ones are “official” ones.
Personally, I use kbin because it seems to federate with the other services more easily. I see so many posts from other Lemmy sites on it, plus it runs pretty well. I also like how it gives you Fediverse-friendly URLs for sharing, with makes it easier to post things from Kbin and Lemmy on Mastodon.
Elireum