I don't have a diesel but do have a front mount. A few of the pro's are it can mow under things, tackles hills fairly well (I water filled my tires, it climbs very well going up hills backwards tires filled or not), it rides smooth, multiple attachments to fit up front (the dozer blade for the front pushes snow very well) and the mower leaves a nice cut.
A few downsides: it seems like it blows more dust on you than a mid mount, especially if you are discharging into the wind, it is a heavy machine that sinks when it gets stuck, there are more moving parts to maintain or replace (deck gearbox, prop shaft under the unit, another set of caster wheels). To me everything on a Grasshopper seems to only fit a Grasshopper mower and seems to only be found through Grasshopper parts, ie: not a universal part. Take for instance the deck casters.... I can find them all day long in the right size but all the universal ones use a different bore diameter than what Grasshopper uses, same with the pulley on the prop shaft in the rear on the unit, same with drive wheels and drive tires. Despite this non-commonality I have found that when you get the non-universal type replacement part it typically isn't junk... may have been why Grasshopper built them this way