Okay so this debate is more or less a choice between XMPP and WebRTC. As a Mozilla contributor, I’ll contact some WebRTC guys asking if they can come here because I think we do not have enough knowledge to take a decision.
Anyway, here are the arguments for the moment:
XMPP is far more mature and supported than WebRTC, no doubt. WebRTC works on only few browsers for the moment, and this is a problem. Moreover, specifications can change because the techno was not released in stable for the moment.
XMPP is used by a lot of network (Jabber, GTalk, Facebook…). Unfortunately, Facebook is completely closed and Google started to close gtalk too (you cannot add a gtalk contact from another xmpp account for few weeks now). Anyway, there are a lot a websites / services (jabber, movim, libertree, etc) which used XMPP, far more than WebRTC and there are desktop clients for XMPP too. So for the moment, XMPP wins. In the other hand, it’s possible that WebRTC becomes the replacement of XMPP in the future…
About development, we do not know enough WebRTC to compare to XMPP implementation.
About pod administration, has said, XMPP is more complex than WebRTC. It needs another server, more sysadmin stuff, more server bandwidth / power, special configuration (ports other than 80)… and is not completely decentralized as it needs to use a server.
Remember, in a perfect Diaspora world, everybody has his own pod under his bed, in a raspberry. I see the server part becomes more and more complex with the time, and I don’t like that. WebRTC totally solves this problem by processing between browsers directly.
Here is the killer point in favor of WebRTC. Chatting, audio, video, file sharing, conf call… (remember, this is “the” killer feature of g+, officially…). This is AWESOME.
Moreover, we are in a moment where companies are trying to put social in them. If we add such features, Diaspora can be interesting for them. And companies can put money / developers in the projects which interested them. This is a really important point, we can maybe find a business model here (and we need one!!).