E.g. relative to the author's script, tarsnap get you automatic deduplication across backups... which, if you're like me and basically generate more and more data, allows you to store lots of historic backups at basically no overhead over just storing today's data.
Tarsnap does have real downsides - restores can indeed be slow, bare per-GB cost is high, and "like tar" is not a user interface that everyone will like - but there are definitely upsides, too.
Also, good encryption and security; e.g. Tarsnap is trusted by Stripe (https://www.tarsnap.com/testimonials.html).
Tarsnap does have real downsides - restores can indeed be slow, bare per-GB cost is high, and "like tar" is not a user interface that everyone will like - but there are definitely upsides, too.