Just got the new Four Wheeler magazine, and they had another INDEPENDENT test with all three manufacturers involved (3/4 ton Crew Cab 4x4 diesels), and guess what......their results were different. Ford 6.7 - 1st, Ram 6.7 - 2nd, GMC 6.6 - 3rd. The test included towing identical toy hauler campers up and down steep grades, unloaded highway driving, and offroad driving. So, I guess it all comes down to what you are wanting out of the trucks as to which one will come out on top in any given comparison.
I looked for a link, but don't see the story online yet.......if you want to read it, pick up the new magazine, I guess.