A zero turn radius mower was originally made to turn within the width of it's own mowing deck. In other word's, it could get to the end of a row and turn around without making that big loop that yard tractor's make. That was the main point of those machine's. Now they have become more of a "must have" even though they really aren't a necessity in most case's. Unless you are mowing in tight space's you probably don't need one, and you do pay more for those thing's. You need a rider though, that make's mowing in August much more tolerable.
Do you know what kind of grass you mow? This make's a big difference in how hard your mower work's. What height are you mowing at? Do you want that manicured look or do you just want to cut the grass once a week and be done with it? The answer's to these question's can easily make a $1000 worth of difference. Good luck.