Hi Marty,
I'd go 6 cyl every time unless you're doing a hell of a lot of loader work. The 6 cyl will have more grunt as well as being slightly heavier, which should theoretically provide more grip. Usually a 6 cylinder won't be as bouncy because of the slightly longer wheelbase. Are you going 40 or 50 km ?
Good on you for sticking to your "Case" guns. I too believe that supporting your trustworthy local dealer is important. I've no doubt that John Deere's are good tractors, but, are they really worth the extra 10 grand ? Probably not !
Let us know what you decide.