I say it depends on what you are looking for. Depends on your “threat model” – among other things.

For example, if you are looking for something more private (smaller chance on linking identities with digital footprint, smaller chance on identifying a person, etc), I suggest SimpleX. They also have a great protocol. Their white paper is worth reading as well. But it might be a little challenging for non-tech people. And the thing is still in development.

If you don’t mind Session’s IDs (after all you can still store them somewhere and change them), it’s a good one. The protocol is promising, and they have a nice white paper. Unlike SimpleX, it’s much easier to set up for a non-tech person, although it’s also in development.

XMPP (Conversations, Monal, etc) rely on a well-known technology, and it is stable. And the interface doesn’t scream “hacking”, " techy" etc.

Lastly, Delta Chat is also a nice project, with a well-known record. The interface looks super convenient and familiar. And the functionality is feature-rich enough in case you want to doe something special.

I would say the thing with IDs (or absence of IDs) is yet another layer that ensures privacy and security. But all of the apps are secure enough. Even Signal is secure enough if you don’t mind exposing your phone number.

I guess the real question is about convenience. That is, knowing about SimpleX, Session, XMPP, and DeltaChat, which one is convenient, private enough, and secure enough for your particular case.