Brave to me means doing the change to end-users even if it’s a noticeable performance hit or “not ready”. Canonical did Firefox as Snap out-the-box default.
Had no idea Mozilla was offering a repo. If I was still using Ubuntu, I’d be using the Snap.
On an unrelated note, since they care about their browser’s presentation so much to be against Ubuntu Snap’ing it, they need to quit playing games and deliver their free privacy-respecting browser on Android in another place other than Play Store or having people trawl some outdated FTP HTTP interface 
I 100% feel that with Flatpaks and yet people like those on Fedora
In Ubuntu’s case with default-providing Firefox as a Snap, there isn’t any additional verification needed with that. If you trust Ubuntu enough to be using it, you probably trust their default repos and packages. Afaik even with Firefox as Snap out-the-box, there’s no requirement to use anything else on the OS as a Snap.