NextCloud integrates into iOS's Files app pretty tightly as a 'storage provider' or whatever Apple calls it. End result is that my password database is magically up-to-date whenever I go to use it in my password manager, probably because Files sees an app trying to access the file, pings NextCloud to say "yo, is this shit up to date?", and then my password manager opens the file. I don't have to worry myself about background sync and such.
I didn't have to do jack shit to open the database the first time; the built-in iOS file-picker that came up let me select nextcloud as a source, and then my password database. Done. It is two taps to get that database open now - one to hit "passwords" in the keyboard area, and the second is me TouchID'ing to unlock the database.
Looking over the Mobius faq, it appears to be vastly inferior, with no guarantee your files are synced at any point in time, and you have to manually push files from Mobius to Files, and then access them in apps from there:
> iOS apps cannot access each others’ files. This means you will need to copy files in and out of Syncthing using the Apple Files app.
I wouldn't do that even if the software was free. And they want me to pay for that? No?