The most powerful thing about an npub is its independent existence. It exists independently of client, platform, and most importantly, independently of any legal enforcement system.
That means, with my npub, I can seamlessly transition between clients and platforms which I actively do with iOS, Android, Ubuntu, macOS and with the clients: Amethyst, Primal and Damus.
I know of no other network where this can be done. Power is completely vested in me via my npub.
The other thing I have been experimenting with is Pay-to-Npub (#P2NPUB) where any npub can immediately receive payment via Lightning and received as ecash.
Stepping back, I realize these are the properties that are going to make #nostr win in the long run - independent existence and the ability to receive payments.