@ulfi @delta Whether or how often you use a certain chat app depends on who you can talk to with it. For example, I wouldn't use WhatsApp if I didn't have a friend whose parents won't let them use anything else. And I would use Signal, DeltaChat, or Conversations/XMPP if someone I knew also used that app. (There are actually a couple people I know on Fedi I use Signal with from time to time.)

Now, assuming you and all your friends have both apps, which one you'd use then depends on how comfortable those are to use. For example, if your friends are in a group chat and group chats tend to break on one (cough cough XMPP), you'd pick the other one. If one is slow and drops messages, or is missing some important feature the other one has, such as anonymous¹ messages, chat apps, or formatting, you're going to use the other one. You're right that there is an edge towards DeltaChat on this one, though on occasion XMPP does still win (and Signal sits in the middle).

¹ XMPP MUCs have a semi-anonymous mode where the group's admin can see the members' real JIDs, but other members can't. Maybe you're a woman and you don't want men from your group chat sliding into your DMs. DeltaChat could possibly recreate this using the mailing-list pattern, but standard DeltaChat group chats can't support it.