No way I would ever go back to a garden tractor from a ZTR. Have owned a TORO commercial 23 HP 52" deck in past to cut 3/4 acre yard. Overkill, yes, but I could cut it in 15 minutes and play ball with the kids. For me, it is all about the time savings. My experience is that the ZTRs also leave a better cut.
We recently moved to a home with 8.5 acres, about 7 of which is grass. I stepped up to a 36 HP diesel Dixie Chopper with a 74" deck. This thing is a tank, blows grass clippings and leaves 10-20 feet with X-blades installed, and never bogs down in heavy grass and leaves. It also does this for the most part at 15 MPH, except on the bumpy parts. No way a CUT could match the performance of this beast. I have a New Holland TC33D mainly for moving dirt, mulch, and snow, tilling, and blowing leaves in the Fall. The Goossen blower I have for the tractor acted up in the Fall and this ZTR did just as good a job (maybe better with the added maneuverability) than the tractor. I cut my 7 acres in about 50-60 minutes, again leaving me with time to spend with the kids. A CUT just would not be as maneuverable as my DC ZTR is, so again it would add time. The stance of the DC is so wide that it is very stable around the hills and pond on our property. I would never go back.