Here's a link to the Nebraska tractor test reports, which include the Fendt 924/926 and the recent JD IVT's:

http://tractortestlab.unl.edu/testreports.htm

The two machines to check side-by-side, I guess, are the Deere 7920 (IVT) and the 7820 ("autoquad plus" -- a transmission I've never seen), with the exact same 8.1L engine. The 7820 shows slightly better fuel economy at full drawbar horsepower.