I'm currently working on a product that gives you a useful bot for your team chat room (<a href="http://www.getinstabot.com" rel="nofollow">http://www.getinstabot.com</a>, contact me for free beta access), so I've had a bit of experience with the two protocols lately (I'm currently rewriting the XMPP frontend in Go, the architectural evolution has been enlightening and it's a very fun process, I might do a writeup if there's interest).<p>This post looks a bit like filler, it's not very accurate on the details (as other posters have said), and it doesn't have much content.<p>I think the main reason people will prefer IRC over XMPP is one of culture. IRC is for talking to strangers, XMPP is for talking to people you know.<p>Because of this, various company chat services are gearing towards supporting XMPP, because people usually already use XMPP clients, and the whole environment is less "let's look around the server and see what channels are interesting" and more "I'll just make a channel here because everyone has a client that can talk to it already.".<p>Both technologies are great, and you can use them pretty much interchangeably, but each serves a different target market. That's the biggest difference, in my opinion.