The main point of Nostr identity is not that it would be more or less secure (there can be an argument made that because you can't change keys, identity theft is total, you have to start over).
But Google can cancel your account. There's a story of a guy who sent a photo of his kids penis to his kid's pediatrician to quickly diagnose a rash and the photo was flagged and his account disabled. He couldn't access his email or any website where he used google login.
Your google account can be cancelled, but you can still sign messages (and thus login) with your Nostr key.
The signers keep the key hopefully safe.
