I like that it’s a separate application. I had issues with the way OneDrive integrated with Windows/Office and conflicts with my corporate OneDrive account (this was a while ago, this may have been fixed).

I always prefer to have a full local copy (Google Drive, which a use for specific data has been really annoying with this) without using Cloud Files API or any extra features. A literal cloud sync of specific folder, nothing else.

I mostly use Dropbox out of habit (and because I have a grandfathered account). I’ve been meaning to switch to ProtonDrive (already have a paid account with them for email), just haven’t got to it yet.