Doug:
As you've seen, we Power Trac types have a considerable amount of brand loyalty. It probably comes from the fact that there are so few of us on the board compared to Kubota, John Deere or New Holland owners. (As far as I know, there's only one active Earth Force owner, but he outnumbers all of us.)
As I noted before, I first got on to Power Trac by searching the net for slope mowers. They are certainly not the only choice.
For hill work, on any machine, the characteristics to look for first are low angle from the CG to the effective tire patch, all wheel drive, and good tires. You also probably need a bit more power than is required to perform the same functions on the flat.
Most compact utility tractors are deliberately designed to be fairly narrow, since getting between obstacles is a more common problem than slopes. CUTs are also fairly high, for ground obstacle clearance. You might consider posing questions to some of the innovators on the board about maximizing a compact tractor for mountain use. For instance if you get a 4wd JD 950, what will happen if you put smaller wheels all around, keeping the same front to back circumference ratio as stock? Then, can you put on duals, to widen the track, lower the cg with liquid fill only to the axle line, add weights low on the frame, etc.? What mods really help, and what will interfere with certain implement use, etc.?
Despite the Power Trac specs, I don't recommend that anyone work on really steep slopes. I haven't measured mine, but they're probably about 20%, which is enough so our conventional 2wd tractors have occasionally gotten away from us, but fortunately not rolled on anyone. As ByuBill has pointed out, even if the grade is theoretically workable, throw in some holes, some leaves, some water, some rocks, some fallen branches and some trees, and you won't be doing much safe tractoring. As long as your main limiter is the pucker factor, you can assemble a good rig for those workable parts of your property for well under new Power Trac prices. (You can also spend more, adding implements, etc., even if you start with a less expensive tractor.)
The next time you go to your place in the mountains, you might want to stop by a couple of dealers in the area, and ask them what machines and what modifications have been successful in the mountains. You can be sure there are already conventional tractors, some old 2wd Worthingtons, some John Deeres, Farmalls, Fords, etc. operating in areas that old men like me won't go near.