The 4710 had some changes from the 4700. JD removed the double brake pedal arrangement. my 4700 has a pair of pedals (L & R) on the left of the operator platform, and a single brake (master?) pedal on the right. The 4710 has only the pairing.
The 4710 dropped the 4700's pull-up parking brake lever/handle left of the seat and had a stupid little pull knob below the control panel. All in all I felt the JD engineers were assigned to reduce the costs. There were other small changes that I've forgotten.
The 4720 went back to a pull-up brake, and improved some features, like the adjustments to the 3-pt swing arms. Wish they would make the seat swivel side-to-side like the NH's.
You can find threads about the front axle leaking oil, about the dash bezel fogging up, and I had to take mine to the dealer for tightening the upper bolts on the engine to fix another oil leak.
And isn't the -20 a different cowl design that enables basic maintenance eg checking oil, than the -00's and the -10's?
If I wasn't livin' easy on SS, I'd jump into a -20 tomorrow.
Jim