PSA: simpleX was designed for small groups and 1-on-1 chats, not 100+ member channels.
It's not a telegram replacement, but a signal/session replacement.
Difference to session: no shitcoin, you can optionally use tor on the network layer (instead of the dubious and unproven lokinet) and unlike session, there's no persistent ID.
Think about it like bitcoin keys. Session/nostr is always reusing the same one. Even with e2e encryption, a lot of metadata about your social graph gets leaked. SimpleX does not reuse keys, identities are more ephemeral.
Compared to keet: it's not p2p (so it actually works), it uses self-hostable relays (like nostr). This helps you prevent leaking your IP to your chat peers.
