I considered purchasing a JD4100 when tractor shopping. Nice tractor. Base price back around 2001 was $12,500 for the tractor, then you had to buy implements. $11,000 for the tractor, mid mount mower and a snow blower with only 500 hours on the tractor does not sound like a bad price, to me.
I believe the JD4100 would also have better traction and much more pulling power than the PT425. It has a range selector and I believe if you put it in low range and barely touched the forward pedal, it would pull a PT425 all over the place. Very nice machine.
I don't know how it would do on side slopes. That is probably why the owner only mows up.
However, some of the reasons I did not purchase it were:
A. I sat up so high on it that I felt top heavy. Probably just a misconception, but I felt that way, none the less.
B. My knees hit the steering wheel. I'm only 6' tall and it was uncomfortable to sit on it.
C. It cost $12,500 without any implements. I got our PT425 with two buckets, 60" finish mower, 48" brush hog, 60" power angle snow blade, pallet forks, loading ramps, extra set of blades for the finish mower and delivery from Virginia to South Bend, IN for... $12,500.
And some of the reasons we purchased the PT425 were:
A. It was more maneuverable.
B. The quick attach system makes it so much more productive than a 3PT hitch.
C. Stability on side slopes. Low to the ground, yet ground clearance doesn't seem to be an issue as it articulates AND oscillates, so all four tires stay on the ground when a conventional tractor would be on three wheels, or even two.
D. Simplicity of design... this was probably the biggest factor.
I asked before and I'll ask again, did you see any of the videos on our website of the PT425 in action?