 The downside to dealing with a third-party website, of which there are hundreds, is that if anything goes wrong with, say, your hotel or airline reservation, your hotel company or airline often can't help you because you didn't book directly with them, and you may not receive loyalty points if that's important to you as well. Are these sites cheaper? Sometimes. I recently checked out a Paris hotel for a June stay. Expedia quoted me a nightly rate of $452, just a couple of bucks cheaper than the hotel's own website.