I am not really wanting a 1500 or a 3500, I am more headed in the direction of a 2500. We do haul round bales and wood in the bed ext.. I LOVE Silverado's!!! Our 6.5 was a Silverado, I loved everything about it, it had no work done before we bought it so it made it to 300,000 miles with out any work at all. It held up to a lot of abuse.
With a 2500 (250) the motor would be a 350, 318, or 360 I believe, and I have heard with all of them 15 mpg is as much as your getting, and that is with out a load. I like diesels if the body doesn't have a lot of miles. Since the motor doesn't seem to need as much work and they have a lot of power, pulling a trailer doesn't affect mileage to bad. We don't make to many long trips, but we do haul/pull quite a bit. 4x4 is a must around here. We are buying used, and the cost of a diesel isn't much more then the cost of a gas.
My main thing is which is cheaper to drive.. a gas 2500 or a diesel 2500.