The UI is really nice, and it's the reason I picked Kbin over Lemmy.
I can browse and interact with Mastodon from here. Right now, there's still a lot to be desired, but I still prefer the Kbin microblog tab over going to Mastodon and browsing there.
Kbin isn't flooded with memes. I never use the All page with federation on because there are just so many memes and shitposts from Lemmy.
Maybe it was, for a slew of things other people have already commented thus far, on the login part, as well as the extra connectivity with me being able to view and follow Mastodon profiles, from this platform's comforts; the latter part makes it look like I'm living in this breathin' and thrivin' town cooperative, despite their geographies, a bit more than the average teenage internet user.
I guess one pro to decentralized federated instances is the fact that noone can block them completely. And if one gets blocked, another one can spin up and deliver the same content.
...inline images, assuming that still works. I store my images on IMGBB which gives copy and paste code for the images, and this works here but not on Lemmy.