Is there any statistically-significant data on which backup applications are the most reliable? I'm not married to restic, but I'll judge it by first-hand experience in the absence of anything else.
Not really, no. It usually goes like in this thread: Someone had a problem with software X and switched to software Y. Someone else had the opposite experience. It's worth pointing out that Borg and other hash-deduplicating backup tools regularly find faulty hardware where other backup tools wouldn't notice the data getting corrupted (e.g. many people advocate for "plain" backup tools like rsnapshot or just having an rsync cronjob, but all of these are unable to check the integrity of backups). Sometimes, users point to the backup tool (sometimes they're right and it's a bug, but usually it's a bad stick of RAM or a hard drive loosing a few bits here and there).