Adding to all the previously added reasons, there's also no native mobile app yet for Kbin, and that seems related to having no API released yet.

That is hopefully going to change soon since at least 2 apps are being worked on by the community - This unnamed one with the goal of being like Apollo, and Artemis which seems to be looking for beta testers - besides the hopefully soon-to-be-released Official Kbin mobile app by the Kbin team.

Kbin's docs for self-hosting are pretty incomplete. Lemmy's docs are also awful but since they have a docker image and an ansible playbook, creating new instances is easier.

I'm not sure if this is why, but another post here was saying there's been a ton of bot sign-ups for Lemmy: https://kbin.social/m/lemmy@lemmy.ml/t/76632/Almost-90-of-the-accounts-on-lemmy-are-now-bot#comments

i like them both but i can see how users would prefer Lemmy's UI as it reminds them more of Reddit (this is just what i've heard a lot on this m).

I still prefer kbin.

I know the difference is partly because Lemmy was a larger platform, and is better known but the growth of Kbin seems suprisingly flat while the community seems to be getting more and more active?

Precisely that. Moreover, Kbin is more fresh than Lemmy (Lemmy seems to have been around for a while longer), and Kbin still lists itself on the website as an early beta.

OTOH, there were already more Lemmy servers to begin with, while there were no third party servers at all iirc when the Reddit migration started.

Lemmy has a bot problem, they gained over a million users with zero activity in like a week due to the lack of account verification.

1- Kbin is newer and less known and more unstable

2- The top five growing Lemmy instances are full of bot/spam accounts

In terms of content posted, I'm not sure that is the case.

In terms of users, there's just been a massive surge in Lemmy users over the last few days - far outstripping the growth in users that happened over the initial Reddit blackout period - which is believed to be because of bots on instances that don't have controls around sign-ups.

i think its opposite

When I went to sign up for the fediverse, I tried kbin first, but signups were broken, so I just chose the next thing on a list of recommendations I found (outside of any reddit posts)

For me it's the ecosystem. Lemmy is more mature with its API and app ecosystem.