The biggest difference is that Keychat's one-on-one chats have forward secrecy, meaning that if your key file is compromised, hackers cannot decrypt your past or future messages. In contrast, 0xchat's default message encryption (Gift-Wrapped DM) does not have forward secrecy.

“0xchat Secure DM

Currently, we support three types of direct messages (DMs), Please review the provided links for a deeper understanding of each DM type:

NIP-04 DM
NIP-04 DM is the most widely used DM type in nostr, but it is not our recommended option currently because NIP-04 is not private in terms of DMs. Even though the content is encrypted, it leaks a lot of metadata. We do not use this DM type by default but are compatible with NIP-04 DM from other nostr clients.

Gift-Wrapped DM
Gift-Wrapped DM is our default and recommended DM type. By using Gift-Wrapped for event messages, it minimizes metadata leakage. Not only is the message content encrypted, but the sender and the timestamp are also concealed. Moreover, the encryption algorithm employed is the latest audited NIP-44 algorithm.

Secret DM
Secret Chat is our third DM type, an extension of the Gift-Wrapped DM. Since Gift-Wrapped DM does not support forward secrecy, if a user's private key is compromised, all DM messages could be recovered. Therefore, we added a NIP-101 key exchange protocol to ensure each message session uses a different receiver key, securing forward secrecy. Additionally, we have incorporated the option to select a fixed relay for these sessions, allowing messages to be transmitted through a single trusted relay for both parties.”


https://github.com/0xchat-app 

 Thanks!