[pkaler]

XMPP is much more extensible than SIP. Presence, messaging, and IM work much better in XMPP. There are extensions for archiving messages, return receipts, etc. There are extensions for file transfer.

There are extensions for vCards. There are extensions for PubSub.

XMPP works over HTTP using BOSH. It can also work over SOCKS.

Apache/Google Wave uses XMPP for federation. It is just flat out more extensible and featureful. Just like the acronym stands for: Extensible Messaging and Presence. It does a whole lot more than just IM or just VoIP.

http://xmpp.org/xmpp-protocols/xmpp-extensions/ http://en.wikipedia.org/wiki/Apache_Wave#Federation_Protocol