This might be part of reason for the lower price on the 6D series:
TractorData.com John Deere 6100D tractor information
Made in Mexico
Not sure how I'd feel about only having 9 forward speeds.
My wife and son really like their new 5065M 16F/16R with Power Reverser. They had intended on buying a 4WD but when they found out about the 5065M 2WD with everything they wanted and the price was $32K they couldn't turn that deal down. Friend of ours bought a new 5115M pretty much loaded and really likes it but says he has it weighted to about 12,000# now and it's just about right but with a full scoop of dirt it still feels a tad light in the rear.