I am interested in building a realtime desktop like app (something which gmail is good at), So I am interested in knowing what are the options, I am aware of socket.io and XMPP but still what is your suggested option when we have lot of traffic and data to push to client.
Also is Gmail using XMPP for pushing new mails to client?
You may want to look at this blog post : http://blog.superfeedr.com/realtime-web-technologies/ that I wrote a couple weeks ago.
In a nutshell : it really depends on what exatcly is that that you’re trying to build. It is also important to understand how “verbose” would be the communications that you mention : 1 message/sec or 1 message/day.