I have the 'bigs' and when compared to the 'smalls', here's some of my feelings.
If you load the tires you get about 100lbs more each.
The bigs use different wheels. The combination of different wheels with different offset, plus the extra width of the bigs will change your interference distance with the 3pt. sway links. (my reading is only 3/4" between the rim and the link,that's why I'm buying spacers).
The bigger diameter will mean a change to the tire size in the tractor's computer controller. The default size(circumference) in the computer is 2972 mm). The bigs size is 3287 mm. (essentially if you don't change it the tractor acts like its acceleration is in 10% overdrive(weak off the line)...I complained to my dealer after a couple of days use and the tech came out with his JD computer and made the change).
If you want the looks, not the functionality, and feel like laying out more coin for the new wheels...then the bigs are what you will probably get. But from a functional view I feel the smalls get the job done.