If you are looking at new diesels, the fuel economy has suffered due to all the emissions put on it. Plus, the added potential high expense of repairing the system after it goes out of warranty. Then there is the higher expense of maintenance.
Gasoline engines are cheaper to repair and maintain. They are very capable of going 200+k miles before needing work. They will have to downshift more than the diesel and will get less fuel mileage. The fuel mileage is offset a little by diesel costing on average about 10-15% more (right now in my area, diesel is 42% more).
General consensus is that unless you put a lot of miles on the truck, pull heavy, or pull often the gasser will do the job just as well for about the same cost. My detailed analysis I did says the gasser I just purchased will cost me about $500/year more to own over the next 6 years based on 20k miles/year @ $4/gal for gas with a 10% premium for diesel fuel. At current prices of $2.20 gal with a 40% diesel premium, it will save me about $600/year. But we all know fuel prices won't stay this low for very long though we can hope.