I have had all three,2002 Ford 250 4x4 srw, 2011 Chevrolet 2500hd 4x4 SRW & now 2012 Dodge Ram 3500 4x4 DRW, all diesels. All three are great trucks, but my current Dodge Ram is more solid and just that little better, well appointed, than the others.
Please go with DRW, get diesel, 4x4 and for towing a rear differential ratio of 4.1.
There are many things to consider. Take your time. Get vehicle with under 80,000 miles and check what it did and has it had regular servicing. Get engine, transmission, diff, brakes and cooling system thoroughly inspected by mechanic you can trust. Has vehicle had an accident?
What is the condition of body work, truck bed, mirrors & glass.
Good luck!