Unless you have a heavy trailer and it sounds like you don't, I think gas is the better choice. We upgraded from an F150 to F250 with a V10 last year and thought about a diesel at first but that idea didn't last long. A diesel is more expensive to buy and is more expensive to maintain over time. More to go wrong and when you hear about various diesel engine problems with different makes and models, gas seems like a better option. Diesel engines *can* be noisy and is annoying in a CG.
Diesel fuel can be harder to find while gas is everywhere. Lower fuel cost for diesel is a big plus though.
We absolutely love the V10 in our F250. Plenty of power and torque and it's very smooth. Gas mileage on short local trips isn't the best, but when towing, mileage is in the same range as everything else. The V10 was only available to 2010.
I've heard that Ford is planning to offer a Cummins diesel in the future. I'm sure it won't be cheap.
One thing I might add is that if you are wondering about getting a 4x4, I wouldn't unless you really need it. They are higher off the ground and the weight of the extra drivetrain components takes away available payload capacity.