I can only compare it from a user experience point of view. I tried duplicati for my windows laptop and was never quite happy. Kopia just worked from day one. The front-end still has a few bugs here and there particularly if you on windows electron eating sockets, WebDAV mounts not always working), however the backend seems very reliable (only did one full restore, but I also did not note any reports).

It still has a lot of potential, IMHO. You e.g. find some hints how to use it with AWS storage tiering in the docs.

I am just a very happy user!