Matt,
I've come at it from the other angle, starting out with a Gravely 50" rider, which cuts field grass quite nicely, to a 61 Ferris Zeroturn with the full suspension and shock absorbers, which reduced mow time by about 40% or more. ZT's are made to boogey and if your land will allow you some speed safely, you will be amazed how fast you can mow.
And when you are done you are going to be pretty tired and sore if you've been going full blast. Zeroturns remind me of driving a corvette, fun, high performance, but you always have wet underarms when you're done, because you've been working at it. I didn't find the zeroturn relaxing at all. In fact I'm now going "back" in your reality to a compact tractor, which does ok and boy is the ride infiinitely softer with the bigger tires just rolling over the old furrows, instead of shaking me to death on the Gravely, jiggling me on the Ferris, and almost nothing on the tractor. I'm 62 with a bad back so comfort drove my decision. Just keep in mind there are tradeoffs. If you want to boogey, you will expend some energy keeping up with the machine.
And unless you are very careful, ZT's will dig up your lawn on turns in any kind of wet weather with a big heavy machine.
I hope this helps you.If you prioritize speed and performance, a ZT is the way to go. I just sold mine, it plain wore me out. For field work, having a steering wheel seems to be a much better idea. For lawn work, if you stay focused remembering you are mowing at quite a clip, the ZT will really get the job done. But, no steep hills with the ZT and if the grass is wet, you have to be super careful driving a ZT, much more than a tractor or garden tractor.
I personally slid down a wet sand mound behind my church's parking lot, and totally out of control went through our neighbors split rail fence. Lots of splinters, but not a scratch on the mower. Just my pride hurt, and frankly when you lose all traction, it will get your heart pounding, because you are like you were at six years old with one of those saucer sleds, pretty hard to steer.
Your "old" tractor might be slow and inefficient, but it has its virtues for sure.
btw, I'm a retired insurance agent, and volunteer fireman, and have seen a lot of accidents in my time. Including one last fall where my close friend slid on his z turn and flipped into his pond, with the mower coming down on his head. Lucky he lived, with many broken bones. The point of this that just like driving a fast car, things come at you faster, and you can get out of control faster on a zero turn than most other things you can drive, in my opinion.
ever thought of a wing mower, like a Swisher? I don't use it much but my Gravely gives me a 90 inch cut. Just an idea if the land allows it.
