youtubevanced.gg is definitely some sort of malware. It redirected me to a "your computer is infected" scam.

The only official one is neither of those sites, it's http://revanced.app/. Anything else is probably a version patched with malware.

If in doubt I recommend looking at either Wikipedia or github for canonical links.

Revanced isn't big enough for a Wikipedia page but there github profile links to the official pages:

https://github.com/ReVanced