I’m afraid that my experience of XMPP (admittedly with non-technical users) has been the exact opposite of yours: all sorts of reliability problems and issues exchanging media (images in particular). I have tried several times, and been forced to give up - non-techies have a pretty low tolerance for anything that requires investigation and/or debugging effort to get to work, and XMPP has turned into a complete non-starter for me for this reason. By contrast, Matrix has been pretty reliable.
Also a grateful shout for @cy8aer and bluepill: I depend on it even more now that the Android apps are starting to require Android 5 (I am using an Xperia X).