Briar is frankly useless.

It won't talk to nearby phones unless they explicitly pair with you, the other features don't give any difference compared to using nostr over Wi-Fi and internet.

Geogram just talks to anyone in the Bluetooth distance without manual pairing. Then it uses internet like a normal messenger or radio walkie talkies when that is what you have (no internet, long distance off-grid).

Would say it is the only messenger that can directly talk to satellites (for free).

Furthermore, it isn't just a messenger. It's the base tool for off-grid communities where they can host websites, receive emails, host pictures, share files and keep a blog. It would be better described as an off-grid radio server.

When the internet stops being available, this tool makes sure the smartphone in your pocket continues to be useful and be used.