Matrix clients are simple, easy, and nice to look at. The matrix server might need more resources, but it comes with everything out of the box. There's no need to fiddle with extensions and their weird naming, and hope that the other server/client also supports the extension. Also, are there bridges to other protocols?
I remember trying to get encryption working on Pidgin and it was all around a bad experience.
XMPP might be as powerful or more powerful than matrix, but nothing about it screams modern. It's like IRC for Gen X'ers.