I actually prefer kbin.(social). It hasn't had nearly as much downtime and errors and whatnot as I've experienced on lemmy. Which is remarkable since Lemmy has been around for a few years whereas kbin is fairly recent.
Like, there are always growing pains, so I get it, and with all the influx of new users there can be issues, so not a big deal.
I think Lemmy's more popular mostly because for whatever reason it's the catchall name for the fediverse right now. IDK if there's any like (very mild) astroturfing going on, or the name is just catchy, or what.
Yeah that's the main issue w/kbin.