I recently got an MX, 52hp. That's a good size for mowing fields. I got a 2m (6 foot) flail, which does a good job of taking the top out of it. A flail is a bit easier on the machine than a rotary cutter. Another option is a batwing.
To my mind, width is king in this kind of mowing. I'd rather mow 5mph with a 6 foot mower than 6mph with a 5 foot mower - much easier on the body.
An L will do the job, an MX is quite a bit more tractor for not much more money.
DPF I don't think is a major issue. Even with light duty tasks, there's no real reason not to run high RPM. I'm lucky in NZ that we don't have DPF on our MXs, conversely we don't get a whole lot of the fruit that you guys get - we basically have a 10 year old model with manual clutch (even on the HST), and pretty basic appointment.
Anyway, a long way of saying you probably can't go wrong here, but I'd look at a bigger machine if I were you. And look at a flail rather than a rotary cutter - they don't stick out as far as a brush hog, and so they don't push the machine around as much.