Upfront cost, the cost of DEF and higher cost of diesel fuel, as well as costly maintenance needs too be considered. So much smog equipment on diesels these days.
For basis day to day, mileage is getting close between gas and diesel, diesels mileage drop off less when pulling heavy loads, if that is your intended use. Resale is always better with diesels.
I have a cabover Fuso, the dealer tells me the gas cabovers, all brands with a 350 GM outsell diesels 3-1 now.