I'm not a big Brave user but I can say that Mullvad Browser is more private than Brave overall because no data is collected at all by Mullvad, Mozilla, or Tor Project. Brave does collect some data, although it is 'anonymised'. Also, Brave can be used as a wallet, it can sync, and it can connect to Google's Safe Browsing service - These can all be used to track you and a certain degree of tracking is required by those services to function correctly. As usual, it's a trade-off between features and privacy. It's also worth noting that Brave is a Chromium-based browser, so if you want the Chromium experience (a little faster and a little smoother) then it's a better browser than any Firefox forks. But if you want the Tor/Firefox experience (perhaps for more privacy but a little slower and not as pretty) then Mullvad is the second best Firefox-based browser for privacy, in my humble opinion. Unfortunately, Mullvad Browser isn't available for mobile yet though.