In my experience (2017 MBP running Mojave), it is much, much faster than Firefox. I have lots of tabs open, and my fan almost never kicks on anymore. With FF, even using ublock and even a pihole, the fan was constantly at full throttle. Maybe I was doing other things wrong, but switching to Brave has made a huge difference for me. I say this as someone who stood by FF for a decade and a half.