I was using PhotoPrism for a few years and switched over to Immich and am very glad I did.

- There was no good mobile backup story. State-of-the-art was WebDAV sync and import delays which would truncate files and other issues on back connections. It also made deletion risky.

- The UI had lots of things that felt very opinionated for a very specific workflow that seems niche. Things like auto-adding generated titles and other things.

- The face recognition is much worse, especially for non-white faces. Even detection didn't seem to have a good setting that would reliably identify what is a face without way too many false positives.

- Immich's semantic image search is way better than what was on PhotoPrism where it seemed to just find a few tags.

- PhotoPrism had lots of UI quirks like the persistent selection that almost never worked how I wanted it to.

Lots of other odds and ends as well. There isn't anything that I actually miss from PhotoPrism.