Resource usage in general, especially server side? Although XMPP clients also seem to win too, cf [1] (debatable methodology in this link, I agree).
And this is not "implementation detail stuff", by design serving Matrix is resource-hungry, while serving XMPP is very lightweight. Others have phrased it better than me, something along the lines of:
> Matrix is a distributed, eventually consistent database; XMPP is just message passing.
Both have their own merits.
But you know all of that Arathorn ;). I'm replying for readers anyway.
