I found Restic slower in general, though Kopia is not super fast either when you have many backup sources (in my case I have 30+ separate directories I am backing up; Kopia works amazingly fast per single directory but make them 30+ and it's not as fast because it's basically going through them one by one and it's NOT going through them in one pass, sadly).
Initially I thought this was a corporate project and was looking for the monetization model, but then I found https://github.com/kopia/kopia/blob/master/GOVERNANCE.md
I feel like the project might benefit from making their governance model more prominent on the website.