Todd, I have no experience with any of the Cadet ZTR machines. I looked/drooled at a pristine TANK this past winter, but that was it. Here are my thoughts, you KNOW quality when you see it. Look them over good and see if you see any red flags concerning how things are built. Both the engines are respected brands, now we all know everyone makes a lemon once in a while, hopefully neither of those is problematic. Just by the price, neither is a "box store" machine.
Any way your buddy can let her drive them (mowing would be really nice if he would permit)? Just how hilly is your property? Around here you see guys running ag tires. My cousin had a Deere in the $8K range and got in a jam mowing near the creek in his yard this year--needed a tow to get out. Since we are not on flat land, I would lean toward the one with the ROPS. Possibly he has sold some of these to commercial cutters that you could contact for an evaluation. Do you know any of his mechanics that might give you an honest opinion?