Expedia, Travelocity, or Orbitz?

I was on CNBC last night (the video is here if you can make it work; I'm on a Mac, and can't). Anyway, we got to talking about third-party booking engines (Expedia, Travelocity, Orbitz) versus the airlines, and how they all want your business. At one point, or so I recall, the host asked if people would really go straight to the airlines, implying that people are brand-sensitive when it comes to booking engines, that they like one and stick with it. Which leads me to this question... Do you prefer one over the other? Why?