It's produced by a "Reputable" company and has a good update process. I can TRUST my software updates from brave.

"Ungoogled Chromium", while FOSS, have no good update method, and since i'm not going to build it myself, I don't have the same level of trust that something malicious hasn't been implanted.

Brave provides similar features to ungoogled chromium and I don't have to support Mozilla or Google and their practices.

Big issue is the trust factor. As well as all the Chrome zero days going out, not having security updates in a timely manner is risky.