I just went through selling my Ford F250 and bought a Ram 5500. I needed big payload capacity to carry my current truck camper and the bigger one which will eventually replace ours. We also tow a large enclosed trailer behind us, so tow capacity was important.
GM currently does not have a Class 4 or 5 truck, so it was between the Ford and Ram. Originally, I was leaning toward a large gasoline engine engine instead of the diesel due to the initial acquisition cost. However, I found that the gasoline engine would limit the capacity of the platform I wanted to purchase plus the reduced fuel mileage would also also reduce my range unless I added more/larger fuel tanks. I calculated operating and maintenance costs a wash between gasoline and diesel for my amount of usage. I had a very good experience with my 3/4t Ford diesel and never regretted my purchase. I preferred the interior controls and seating of the Ford (perhaps due to habit), but each had some unique or different options over the other. Although I initially wanted a Ford F550 Supercab with 60" CA, the pricing difference on the Ram 5500 crew cab with 60" CA was significant enough that I chose the Ram and even added some non-necessities.
I'm coming up on two months of owning the Ram and have no second thoughts about my decision. Ten years with my previous Ford always left me happy with my decision - Time will tell how the Ram fairs, but it's starting out well.