You didn't mention anything about recharge costs, that needs to be in the equation as well. Of course now we need to start thinking about the future costs of electricity vs that of gasoline or diesel,,, too much for my brain, I can't look that far into the future, and if I could they would be sure to change it so that I would be wrong once again.
Last year we bought a Country Clipper z-turn with a joystick. Ours is only a 42" but they make bigger ones. I couldn't be happier, easiest machine I've ever cut grass with. But it does run on gas.