David,
I have no experience with Power-Trac, but I do have a 31 hp Ventrac 4200 with dual wheels, 72 inch deck, and several other attachments. With dual wheels it is rated for slopes up to 30 degrees.
The very first thing I would recommend is that you Measure the actual slopes you intend to operate on so that you know exactly what you are dealing with. Just buy a $5 carpenter's protracter level and place it on a small piece of plywood roughly a foot square on the steepest slopes that you have. It is very important that you know because the Ventrac is rated for 30 degrees whereas the PT 1845 is rated for 40 degrees of sideslope.
You say you had a demo of a Ventrac 4200 with a 60 inch deck, but you did not say if it had duals or what the horsepower was. Based on comments from Ventrac dealers and my own experience I would not want any less than the 31 hp gasoline or diesel engine for steep hill operations. In addition, the tractor is 70 inches wide with duals and, therefore, it would work best with the 72 inch deck rather than the 60 inch deck. I also run the 66 inch rough cut deck in tall grass and weeds with no difficulty, but for such conditions the wheel overlap of 2 inches on each side is not a problem.
Traction and braking performance straight upslope and downslope is important, but sideslope stability is a more critical. Unless you can be absolutely sure that you will never have to make a turn while on a slope, this is the most important factor to consider for steep hillside operating conditions. For articulated 4WD tractors, the driving scenario that provides the greatest challenge is to make a U-Turn on the slope while going straight downslope (and straight upslope). You should be confident that the tractor and deck can execute this on the maximum slopes you measure.
You mention the possibility of needing a backhoe. Ventrac does not currently offer one.
The Power Trac is rated at 45 hp vs. a max of 31 for the Ventrac. The Ventrac 4200 with duals, 31 hp, and a 72 inch deck weighs about 2200 pounds. From the PT website, a PT 1845 with duals and 72 inch deck weighs 3463 pounds. So the PT is clearly a larger unit.
A demo at the PT factory may help you with your decision. Furthermore, if your previous demo of the 4200 did not have duals and a 31 hp engine, I would ask for another demo with these features and 72 inch deck. Make sure the 2 Weight Transfer adjustments are set to Maximum.
Good Luck and keep us posted.
JackIL