A major factor why I wouldn't want to use Kopia (I looked into it) ist that it is opinionated with regards to how your system is set up (old-school unix FS layouts in a "pets, not cattle" way). It assumes the location of config files and does not allow you to change the backup path that's stored in a snapshot's metadata.

That's bad if you want to use it

1) on NixOS (I don't want backup configs laying around in `~/.config`). As Indy famously said: "That belongs in a Nix expression!"

Edit: On a second note: Why have mandatory config files at all? I don't have an issue with having the option or it being the default, but for my use case being able to specify the whole repository config via arguments sounds considerably more sane.

2) with ZFS snapshots (yes, I'm backing up `/path/to/dataset/.zfs/snapshot/<timestamp>/foo/bar`, but that should not be its path in the metadata!)

OTOH, it seems to have the upside that you can apparently alter snapshots after the fact more easily (e.g. if you find out you shouldn't have backed up that gigantic VM image you just moved somewhere temporarily). I leave the decision on whether this is a footgun or not to you.

And to be clear: The ZFS snaphot thing is also a pain with Restic, too. You can hack around it somewhat better with something like systemd-nspawn, but it really shouldn't be that hard.

For context, I am long time Kopia user.

Looks like compression only added in the latest release of restic.

No mounts on windows.

No GUI?

Lack of compression was likely the reason I went with Kopia.