I use both, but overall I prefer kbin.

I like the UI much better (on mobile - I couldn’t even tell you what either one looks like on desktop). The lemmy mobile UI is too disjointed for my tastes - it’s essentially just a seemingly random assortment of buttons for a seemingly random assortment of functions. I’ve tried a few lemmy apps, but haven’t been impressed, and I can’t be arsed to wade through dozens of betas in the hope that one of them might actually appeal to me. Kbin’s UI is fine the way it is, so that’s that to me.

And I like kbin.social’s “All” better than any of the lemmys I use (.world, .ninja and .one). Kbin.social has a pretty broad range of content, but generally without the botfarm instances, which is just what I want. Lemmy world (when it’s working) has too much botspam for my tastes, and while I love lemmy.ninja just on principle, it has a relatively sparse and limited “All.” Lemmy.one’s “All” is pretty good, but the overall feel of the instance is a bit too weedy for my tastes.

And Ernest is awesome.