I've previously used Borg, but the inability to use anything other than local files or ssh as a backend became a problem for me. I switched to Restic around the time it gained compression support. So for my use-case of backing up various servers to an S3-compatible storage provider, Restic and Borg now seem to be equivalent.
Obviously I don't want to fix what isn't broken, but I'd also like to know what I'm missing out on by using Restic instead of Borg.