I've always ( 36+ years ) had open station tractors. I guess its because while our summers can get beastly hot - humidity is most often well below 20%. I don't mind being out in the cold in the winter either - I have the necessary cold wx gear.
HOWEVER - if I had to bush hog on my property - I would be in a new cabbed tractor in a heartbeat. I've seen the dust, ash, pollen, crud, corrosion that is raised when a bush hog is used in our area. It is fearsome. Without a cab - I would most certainly need a full Haz-Mat suit to combat the airborne crap. It is easy to understand how the older farmers in our area have almost all developed one form or other of some type of breathing disorder.
Dusty, grease stained ball cap - week old beard - friendly smile - bib overalls - Mucks - some form or other of inhaler in their breast pocket of their bibs - old style farmers of the Palouse.
Its still very easy to raise the volcanic ash from the 1980 eruption of Mt St Helens on my property - just drive out now during the summer dry period. That cloud behind my tractor is mostly volcanic ash.