Ron, I'm not sure if this is a complete answer to your question, but Agcodealer has put up some snippets of Nebraska tests that show some efficiency comparisons. Look at Fuel Consumption at Maximum Power from the dealer website linked to by Agcodealer's profile. The chart on that page is taken from various Nebraska tests which I was able to locate, but forget the exact models. I was quite surprised to see a dealer show a chart that shows his product as being the worst in the comparison!

edit: I forgot to announce myself as working for a Deere dealer, but also having worked at an Agco dealer in the past. Since this is a biased discussion, I felt I should do so.