Made by the creator of bupstash:
TLDR; Andrew’s Summary:
GNU Tar + gzip + gpg is an excellent encrypted backup option and performed better than I expected. I think tar and gpg is still a great choice for users who prefer to DIY their own backup scripts. With this in mind, we must ask what are the problems with tar that the other tools address? My opinion is that managing incremental backups, deduplication, pruning, and searching backups are far more difficult when using incremental tar compared to borg/restic/bupstash. With incremental tar, it quickly becomes quite hard to track which incremental tarballs depend on eachother and you often need to periodically do full snapshots - losing most of the speed benefits.
As the biased author of bupstash, I am also pleased with how it has performed and hope I can push it further in the future. Restic, while fast at local operation, seems to trail the other tools when network latency is thrown into the mix. Borg is an all-around great tool and performed very well.