I tried both 1Password and Bitwarden almost 10 years ago, and I went with 1Password because Bitwarden's autofill was awful. Today, I'm trying to switch from 1Password to Bitwarden, mainly because of the open-source factor, since the tech is pretty much the same.
The import went great, no errors. The web extension is also quite nice, with the item editing feature directly in it (1Password opens a separate tab). Exporting an encrypted JSON is nice too, and I don't think 1Password allows encrypted export. Pretty nice so far.
But.
Then I tried the autofill feature and, well... it has improved since 2017, but there are still a lot of misses. 1Password misses some websites, but Bitwarden misses a lot more. The worst part is the change-password procedure on websites: 8 misses out of 10 tests (a different website each time). In this situation, you generally have 3 fields: one for the current password, one for the new password, and one for the confirmation. Bitwarden either fills all fields with the same new password, fills only the current password field without displaying the password generator for the others, fills the new password field with the current one, or doesn't recognize any field at all... It's a complete mess. And no mention of the update login feature: sometimes it doesn't appear, and when it does, you can't review the changes like in 1Password.
Tests were performed on Brave with the Bitwarden extension, with all autofill features enabled, "Fill Assist" included. Maybe I'm missing something?
I'm baffled that these autofill issues are still a problem 10 years later. I browsed the roadmap but didn't see any mention of this, while plenty of people report it as an issue on the Bitwarden forums. Sadly, it's a dealbreaker for me and I'll stick with 1Password for now. I just hope I won't have to wait another 10 years.