I have been pleasantly surprised with the architecture of SimpleX and how well it works. Things that make it better than other private messengers:

- It doesn't use a phone number.

- There is no user ID with which servers or a third party can trace messages.

- It is decentralized with a network of federated servers.

- The servers do not store any messages, they are only a transport agent, although they hold messages in a queue until they are delivered.

- Different routes are used for sending and receiving messages.

- You can set up your own server.

- The gui is really polished.

- Supports calls and encrypted video.

- It works.

It has many things in common with Nostr, it just works, p2p messengers have a lot of usability and performance problems, maybe for some things distributed networks are not ideal and you have to resort to decentralized networks like SimpleX.