Firefox is a bit more CPU intensive than Chrome so if your using older hardware or budget laptops, this may be something to watch out for as it can cause excess battery drain.
Brave does not have the typical account-based syncing that Chrome does(Firefox has account-based syncing with a Mozilla account). It uses E2EE-sync that is set up by QR-Code or passphrase. Major issue of this is that if all synced devices lose your browser data, theres not a way to recover it like you could with it being tied to an account.
Also, Firefox doesn’t have access to Chrome Web Store for extensions. It uses the Mozilla Addons site. Brave can use the Chrome Web Store for extensions though.