That’s more for people hosting servers, who are likely to care somewhat.
The whole argument at the top of the thread is "it doesn't matter how easy/good/performant it is to run a XMPP server, if the people you'll want to talk to do not have a decent client".
If I was to make an argument for why someone should switch away from Matrix, I’d just point to how often encryption fails.
That has stopped for me since I started using the element X client (mobile) and Fractal (desktop), which leads me to my "counter argument", which is: Matrix has always sucked in different ways, and it sucks for everyone equally, but at the least it is slowly and constantly sucking less than it used to. XMPP is adequate (not great) for some (Android, Linux) and disgraceful for others (iOS), but unlike Matrix there is no visible progress for those on the sucky side of XMPP.