Kbin does a better job of putting new posts in front of you even before you have subscribed to anything, so I think it is easier to find interesting things to read. Kbin is newer than Lemmy, so Lemmy had the advantage in familiarity for people. More people had heard of it when Reddit's API drama blew up and that gave Lemmy a distinct advantage when people picked a new platform. Kbin also has some annoyances like not being able to collapse comments and vote buttons being at the top instead of the bottom of posts and comments. If someone has written a lengthy comment, I want to read through the whole thing before I decide how to vote and I don't want to scroll back up to get to a vote button. To reply to a post you also have to scroll through the comment section. In some cases it's good to see if someone else has already said what you are going to say, but in other cases if someone is looking for personal stories, you don't necessarily need to read everyone else's story before submitting your own.

Personally I have this kbin account and a lemmy account as well. My Lemmy server seems to go down more often and the default sort always shows the same days old pinned posts from my server admin that I can't seem to hide after reading. On Reddit, I didn't have to switch sort to see newer stuff so Lemmy comes across as pretty stale sometimes even though there is a fair amount of posting going on.