I'm going to write about Keet once they open source.
Keet is peer to peer UDP via holepunching. This has pros and cons.
Pro:
-Faster file transfers and video chat
-Less censored group chats or individual
-One of the few unstoppable group chats that doesn't rely on hiding the server. There is no server
-Avoid government domains
Con:
-UDP packets won't work over Tor
-Not as easy to hide this networking style from global networking surveillance
-Not yet open source
-Other person has to be online for peer to peer
Comparison with others:
Session group chats are on a regular server, while as Keet is peer to peer, so it's more unstoppable for group chat than the other things on this list. Keet also has the group video chats in a way that others do not.
But Keet requiring UDP from your home makes it less private than anything you can onion route. So no Tor even on, or onion routing like Session.