I love this debate everytime it comes up here and on other discussion boards. There is so much missing, including what other tasks, one's aversion to mowing, type of yard/grass/obstacles. As a point of reference I have varied mowing requirements, from dodging trees to "brush-hogging" 4 ac, to a nice 1 ac flat parcel. I have mowed regularly with a 48" Wheel Horse tractor, a 60" Simplicity Sunstar, and my current 60" Snapper Pro (Hydrogear ZT3400 transaxles, a Ferris rebadge). I've mowed with my buddy's massive Gravely Pro with ZT5400 hydro units, and for a while I mowed my other friend's yard with his Ariens 54" Ikon.
Does the ZT save time? Yes, mostly in that I can hit the long straights at 8 mph. Is the ZT better in corners and around obstacles? Yes, but not as much as everyone thinks. In order to prevent the grass smushing from the inside wheel the turns need to be super careful. I could mow around trees almost as fast with my tractors, and never ripped up the grass. What is also missing from this conversation is the grass/soil composition and dampness. My clay soil is most always damp and there is very little I can do but go really slow to prevent grass smearing. In the dry late summer, things are different. Those of you in the dry areas or with different soils have little idea. Wetness and soil also play a role in getting stuck, for which ZTs are infamous. The caster wheels easily make or find ruts and you cannot turn them out of the rut. Not so with regular steering. The commercial ZTs are huge, unnecessarily wide at the rear tires, and weigh a ton.
Unquestionably the Sunstar was the best mower, best lawn care implement, best at everything. Seriously heavy duty STAMPED deck, massive hydro unit, driveshaft for the mower deck, "easy" to remove deck (well, for about 200 lbs or so), easy to service, two speed ******, differential lock, and comfortable one arm steering and throttle control. I only got rid of mine because at 30 years old it finally starting nickle and diming me.