Signal is the most user-friendly option so far, which is also expected, given it's also one of the oldest one of those.

Simplex is also a good-ish option, but somewhat rough around the edges; the biggest benefit is, one doesn't need a phone number or e-mail to start chatting.

Matrix is questionable: it's quite feature-rich, but lacks solid android clients (IMO, fluffychat is among the best so far, yet when I last used it, it didn't handle stickers/custom emojis all that well, for example); as for the desktop/web clients cinny is a godsend due to allowing importing/exporting encryption keys manually, which just works all the time.