I do believe Simplex does a better job in terms of privacy. I just want to clarify: the NIP-44 encryption algorithm we use has been audited. Please check out this report:
https://github.com/paulmillr/nip44/blob/ce63c2eaf345e9f7f93b48f829e6bdeb7e7d7964/audit-2023.12.pdf
Additionally, the NIP-17 DM we use has been merged into the main Nostr branch, which can prevent metadata leaks