I agree with the other guys...it comes down to how you'll use it. If it's going to do some real work hauling or towing, get the 2500 (if not the 3500 depending on what you want to do)

If it's just for transportation, hauling some stuff around once in a while and pulling a boat or light trailer around occasionally, the 1500 will give you a lot nicer ride. The 3.92 in mine seems about right.