I’m looking into hosting one of these for the first time. From my limited research, XMPP seems to win in every way, which makes me think I must be missing something. Matrix is almost always mentioned as the de-facto standard, but I rarely saw arguments why it is better than XMPP?
Xmpp seems way easier to host, requiring less resources, has many more options for clients, and is simpler and thus easier to manage and reason about when something goes wrong.
So what’s the deal?
I don’t think you can pick out any one reason. XMPP is very old and has extensions for a huge variety of features. Many people have experience with older versions which had many major missing features (such as strong multi-device with offline support and server-side history) and a lot of the “hype” has died out long ago.
Matrix is new and made a lot of decisions that really helped its popularity.
We will see what the history holds. Matrix is still very new and maybe the hype will die out and we end up moving back to XMPP. Or maybe something new. Overall I don’t think there are major fundamental differences. I think Matrix making graph sync the core primitive to build off of was a good idea, but in practice I don’t think it matters much.
You say that XMPP is much lighter. But I think that is mostly due to Synapse not being very efficient. Other implementations are fairly light. Even then my Synapse is using fairly small amounts of resources. You should also check that you are making an apples-to-apples comparison with large rooms, media and message history like you would typically see in a common Matrix server.