Brave is similar to Opera. It's not a mainstream browser, and they also want to make money. Dipping into publisher revenue and using some broken BAT crypto currency to reward publishers is not the way to do it. The currency itself is mostly useless and unstable, plus you will be making peanuts compared to even the lowest CPM country in AdSense.
What we need is an ad provider that provides a meaningful experience to advertisers and non-invasive ads to publishers. An entirely context-based, tracking-less, controlled (iframed and sandboxed).
A browser is a user-agent and it should stay that way. I like certain things Brave is doing (such as proxying Google Safe Browsing API requests), but for all this BAT nonsense, I would still stick with Mozilla.