Sometimes the federation is quick, and sometimes it's slow. kbin.social has been wonky with federation ever since I joined haha. it was down entirely the first few days, and now seems to mostly be working (albeit sometimes is slow or misses posts for a while). I think these are mostly just teething issues though, since kbin is very new and just recently scaled massively to a degree that's unfamiliar to the admin. I'm sure things will be worked out in the future.

But your suggestion of joining the instance that you interact with most is probably a good idea. It lets you be "safer" about losing access due to defederation (see how lemmyworld was blocked by beehaw). it removes federation issues (it's all native content), and the users there are probably more similar to your own way of thinking/doing things.

I interact with a lot of lemmy.world threads, but I don't have any intention on migrating there. I like kbin, even if it means missing some lemmy.world threads.