Session is also sus because you effectively cannot host a node, last I have seen. They claim it is “against a Sybil attack” but all it does is making sure only people wih large disposable funds can have nodes, and the effect might be the exact opposite.
Simplex is more interesting in this regard because while I am concerned with initial centralization (the default servers), they made hosting your own easy. But I personally stick with imperfect yet trusty XMPP.
SimpleX is great. BUT it’s not user friendly. Thus general adoption for the average user will be hard. Don’t get me wrong using the app itself is easy but as soon as someone switches their phone that doesn’t have technical knowledge they will loose their chats because they won’t understand the concept of moving their DB. Since you don’t have an identifier like a phone number with SimpleX those people could even lose contacts as a whole since they generate a new DB, hurting their social connections.
That’s the reason I personally never recommend SimpleX to anyone who doesn’t have the technical knowledge to understand stuff like that.