Attached is the latest link to the Roofing Square Challenge.
What they did was install 1 full sq of every manufacturers shingle on a 10×10 Deck to see who really covers a full sq and who gives you a short sq when you install 3 bundles.
Someone recorded the whole installation from cutting open the wrapper to the last nail that is installed. The video is sped up, so its about 17 min long for all 7 manufacturers. You can see clear as day how many sq feet you lose with some manufacturers.