I don't know where's you're at but for health reasons a cab is a must. In some states there is the chance of Valley Fever.
A good friend of mine died from it.
Valley fever is a fungal infection caused by coccidioides (kok-sid-ee-OI-deze) organisms. It can cause fever, chest pain and coughing, among other signs and symptoms.
The coccidioides species of fungi that cause valley fever are commonly found in the soil in certain areas. These fungi can be stirred into the air by anything that disrupts the soil, such as farming, construction and wind. The fungi can then be breathed into the lungs and cause valley fever, also known as acute coccidioidomycosis (kok-sid-e-oi-doh-mi-KOH-sis).
Mild cases of valley fever usually go away on their own. In more severe cases of valley fever, doctors prescribe antifungal medications that can treat the underlying infection.
Another reason I will never drive an open tractor are bees. I had a swarm attack my tractor ( it was a closed cab D7 ) and I swear it seemed like it was a solar eclipse. I mean it was 12 noon and there we so many bees hitting the glass the inside of the cab went dark.
Again depending of the work you do you, if you do any land clearing you have the chance of a tree branch smacking you in the face. With a cab it will be deflected by the windshield.
Now lets talk comfort. If your in the cab 8 hours a day being cool in the summer with a nice radio makes life just a tab bit nicer for that time in the cab .