I've been using Kbin and Lemmy so far and I like both, but Kbin seems much more stable right now. I like kbin interface a bit more and the ranking algo seems to work better (there an issue on lemmy with hot and posts being added that should not be there). Kbin also let's me sort by 3hr/6hr/12hr in addition to normal sorting options.
kbin does seem more stable. It hasn't had issues for the couple days I've been here, while lemmy has gone down quite a few times during the same time frame.