title: longpoll XHR vs iframe
body: <p>I'm implementing typical server-push (comet) application. I'm choosing between two options: the longpoll XHR and iFrames. What are pros and cons of these? I know about the cross-site restrictions and that iFrame is pretty heavyweight component... are there any other differences? For example the "reliability" of the transport or level of control over the component?
  What do you think, is there a single right answer which approach is better or there are use cases for both of them? </p>
  
  <p>Thanks in advance.</p>
  
  <p>P.S. I got a pretty good working XHR implementation, but I want to consider the alternatives.</p>