I think any commercial grade ZTR would be a good choice. For the most part, they all use the same engines, transmissions, wheel motors, tires, seats, etc. what sets them apart will be things like deck design, suspension options, and paint and decals. one more thing that needs to be pointed out is rider position and comfort. My mower has a more upright seating stance, while my buddies scag seems to be more of a reclined or shallower seating stance. all of them will be slightly different, so go check them all out and sit on them and see which one you like best. They will all cut about the same, and then you just need to factor in which brand you like and which dealership you want to work with.
I have a hustler super Z diesel 66 inch and I'm very happy with it. my buddy has a scag cheetah 61 inch and he loves his. it's all pretty much a matter of opinion in the commercial class.