I am using both for enough long time,mutlidevice synchronization it’s nightmare in xmpp,also usual xmpp isplaintext.So when u wanna use encryptions like omemo so far not always guaranteed that ur encryption key will be delivered to ur new device which u connected.Also u cannot control sessions.So if u would be hacked u would not be notified,and u don’t have ability to kick out this dude session.But yes xmpp more light about resources and works faster for now.