You can choose whether or not to show a QR code, or even disclose whether you have one, and to whom.

Mass surveillance is imposed and can't be opted-out from (unless you have an invisibility device, in the case of widespread cameras).

QR codes can also be discarded, or new ones issued. Biometrics (e.g. face structure) cannot be replaced once "compromised". I use quotes for the latter, since biometrics are never secret in the first place (e.g. if we could keep our faces, fingerprints, DNA, etc. secret then they'd be useless in criminal investigations!).