title: UIDocumentInteractionController vs QLPreviewController on iOS
body: <p>Can anyone who has used both comment on "What's the difference, and when should you use one over the other?"  I have spent the last couple days adapting code from the DocInteraction sample to my own app, and the more familiar I become with these two kits, the less difference I see between them:</p>
  
  <ul>
  <li>They both display docs</li>
  <li>They both only present full screen</li>
  <li>They both have "open in" and "print"</li>
  <li>They both can zoom from a small rect on screen</li>
  </ul>
  
  <p>I just don't see any difference when switching between them except the color of the toolbar.  </p>
  
  <p>Of course I'm missing something (or wrong about those other points).  Any thoughts?</p>