So the best technique here is to check one of the traditional sites, and then play around with the new guys and see if they can pull an upset. Then, before you book, check the airline’s own website to make sure it’s not even cheaper there. (And don’t forget that Southwest — by its own choice — doesn’t show up on most sites.) And as long as you’ve popped over, it’s almost always a good idea to do the actual booking from the airline’s site: It’s often easier — and rarely harder — to take care of the minutiae (entering your awards number, choosing seats and paying for extra luggage, as well as changing your reservation down the line if necessary).
I never do booking on the airline’s site! And as much as am always convinced there is some great deal out there just beyond my reach that everyone knows about but me, I honestly have just used Orbitz.com since high school and have never done anything else. I’m also not a frequent flyer anywhere for complicated psychological reasons that can be boiled down to, “I don’t want to think about all the free miles I could have gotten already if I would have signed up years ago, so I am going to ignore that this exists as an option.” Same goes for rewards cards. I would go on but the ways I apply this line of thinking to other areas of my life is frankly a little terrifying.