the only difference is the price of the parts. the 2500 is heavy duty and will be able to tow more than the 1500. and depending on the engine the 2500 may get less mpg. overall it all depends on what your using it for. if its being used for towing heavier stuff or gonna be using it for plowing then your better off with the 2500. but if its just for a every day truck then you could get away with the 1500