I use restic currently. I remember that one of the reasons for choosing it over borgbackup was existence of `restic copy` (so that I can make a local backup and copy _that_ offsite, instead of doing separate offsite backups). I think I had some other reason related to some kind of ease of automation, but I can't recall it.
That said, restic's approach to being used as a FUSE filesystem is somewhat frustrating: it takes a lock on the repository and holds it until the FUSE mount is unmounted. That precludes the obvious approach of having all your (local) backups mounted at all times (or at least having a recent snapshot mounted). I don't know if Borg shares this property.
Can I copy over _some_ snapshots only between repositories? https://kopia.io/docs/reference/command-line/common/repository-sync-to-sftp/ seems to allow me to copy _all_ of them but not some.
@robryk @rysiek I never tried but I think all of them only