Price is a good guide
The best we had on the SWB were the bigger Toros . The worst were the 16 HP victas. (Yankee Email crap).
If you want a really good ride on, it will cost about the same as a small car.
Some of the other big name ones are also crap.
A tractor/slasher combination works exceptionally well on level ground and if the blades are sharp cut as well as a ride-on. If you buy an old tractor make sure it has a double clutch other wise danger lurks.
Lever steer zero turn things are pretty good once you try them.
I do a bit of mowing with a Dixon zero turn thing with a 20 HP Honda. Its pretty good and reliable but it has its limitations on slopie ground if the grass is a bit wet. The wheels are too small in diameter and won't respond by pulling back on one lever to turn, you need to accelerate the outer wheel to turn. Gets hairy going down hill towards the dam. So far I've got soaked once, hit barbed wire fences twice, and slid right of the seat once and ended up on my bum in a gutter.
All good fun, just like the old days riding at Moorebank scrambles.
Cheers pancho