Havoctec
I've been pretty much in the same boat, making the same decision. Was seriously thinking of trading up (4300 to 3720) for more hp. But the one piece hood on the 3720 was a negative, as well as the foldable ROPS. Also, I didn't think the sloping hood gave any more visibility over the 4300.
As well, the 4300 still does everything I want, and I can get along with the hp it has.
Didn't know about the wheel change, and that surprises me as well. But change is what makes old tractors obsolete, and new ones more unique. Engineers have to account for their progress and worth too.