Signal vs SimpleX
Signal is the mainstream, audited gold standard. SimpleX removes user identifiers entirely. Which one fits your threat model?
Both encrypt message content with strong, audited cryptography. The difference is what they protect *beyond* content.
Signal stores a server-side mapping between your phone number and a hashed account, with minimum metadata via Sealed Sender. A subpoena could reveal "this account contacted that account at this time." Mainstream UX, group calls, file sharing all work seamlessly.
SimpleX has no user identifiers. There is no account. Servers route messages between unidentified queues; even a fully compromised server cannot reveal contact graphs. UX is rougher than Signal, but the metadata story is genuinely stronger than any other mainstream messenger.
Pick Signal if you want your friends to actually use it. Most users, most threat models — Signal is the right answer.
Pick SimpleX if your threat model includes the question "who you talked to" being more sensitive than "what you said." For most journalists, sources, and high-risk activists, this distinction matters.
You can also use both. Signal as your daily messenger; SimpleX for specific threads where the metadata matters.