Audio quality when casting (Chromecast Audio) from brave is objectively poorer than when casting through Google Chrome.
Cast Brave to a Chromecast Audio device and run a perceptual sweep. Run the same procedure on Google Chrome. Google Chrome will playback the sweep without any artifacts. Brave will introduce artifacts which sound like reduced bit rate throughout the whole sweep. This issue is audible in all audio files and Youtube videos but easy to spot using a sweep.
Brave and Google Chrome should sound the same using the same procedures.
macOS 10.15.7. Brave [Version 1.15.76 Chromium: 86.0.4240.111 (Official Build) (x86_64)]