Agree on the pathing to a degree, but it seems like no matter where they turned around on a given week of cutting they tore a pieplate of grass down to the dirt. Spinning on a dime to flip 180 with a commercial ZT seems like it will always do that.If you were to buy your own zero turn and mow your yard many different ways then 1 your yard would not get tore up from turning. Landscapers like to leave a stripe in the yard. They usually only mow one or two ways total. Do nut run the same path and turn slower and not as clear cut. If you mow a different path each time you will actually have a healthier yard. Good luck. As far as size a nice 48 or 54 cut would do perfectly for a 3/4 acre yard. Anything bigger is a waste of money. I would not use a B series tractor to mow with. If there is dew or moisture in the yard you will create divets everywhere. I mowed my grandmas yard in 20 mins with a 54 and hers was one acre.
What exact mower did you cut 1 acre in 20 minutes with that was a 54" deck? Assuming you mean a ZT, not sure a lawn tractor would do it that quick.
And no doubt, a 72 or 60 on a B2650 is overkill for 3/4 acre anywhere. But I already have the machine, so part of me REALLY wants to use it. If I was 100% confident I wouldn't ruin my lawn from the weight, I wouldn't have even started this topic.