[Paul F]

Most name brands are fine. Points to consider.

Name brand engine for parts and reliability. Most are using Kohler.
Hydrostatic transmission. Even if you are mostly doing the field, the hydrostatic is very nice. No shifting required, even when going to reverse. Just hit the reverse pedal. But you may prefer a shifter if you are doing just straight field work. You don't have to keep your foot on a pedal.
Big/wide tires - the bigger and wider the better. Smoother ride. I deflate mine to give more of a cushion over the gopher bumps.
Electric blade clutch instead of mechanical engagement.
Tight turning radius. Maybe you don't need this with the field cutting, but if you have trees or other stuff, this is a key feature.
Go for the widest deck. I cut 2 acres (some wooded, some is the yard) in 1.5 hours.
Even with 54", with the tight turning radius, I can get around the yard and the trees very well.
Adjustable deck wheels. Only if you are doing the lawn as well as field. They need to be adjusted to keep the deck from scarfing at the height you like for the yard.
Grease fittings on the spindles is nice. Most don't have it. But the spindles aren't that expensive to replace