A few things I remember: adding new entries was clunkier in k2a because I had to tap multiple times to select things like category/folders that I didn't care about. Bitwarden has better URI matching as I could choose the matching rule. BW has better search, or rather it displays search results in a more useful way. The autofill service also seemed to work more reliably, and I don't think k2a showed the matching logins right in the autofill drop-down menu, but I could be misremembering there.

Ultimately though it was the browser extensions, combined with the self-hosting option, that sold me on BW. None of the Keepass plugins I tried over the years worked that well. BW has extensions for both Firefox on Android and Vivaldi on desktop that are as solid as anything I've tried.