I have to disagree. SimpleX has much better privacy at the moment. NIP-104 will help once it's complete and implemented in 0xchat, but SimpleX may retain an edge in privacy since users have no identity between chats. We could maybe approximate it by using a new nsec/npub in every chat we join, but I'm not familiar enough with the architecture to say for sure if that'd be fully equivalent.

To match SimpleX, you need to have the same encryption (Signal Double Ratchet Algorithm) + post-quantim ratchets (like Apple & SimpleX have done

iMessage with PQ3: The new state of the art in quantum-secure messaging at scale - Apple Security Research

iMessage with PQ3: The new state of the art in quantum-secure messaging at scale - Apple Security Research

We are introducing PQ3, a groundbreaking cryptographic protocol for iMessage that advances the state of the art of end-to-end secure messaging. Wit...

SimpleX Chat v5.6 (beta): adding quantum resistance to Signal double ratchet algorithm

) As well as using pairwise identifiers for messaging queues (separate sending receiving servers and address) which should be done automatically, behind the scenes so users don't have to create a separate identity for each contact.