Im looking to buy a newish used 4×4 truck that can tow an ATV for sure and possible a 18 foot boat (not at the same time) that gets has decent gas mileage. The boats not as big a deal as the gas mileage and atv and if it resulted in getting much better gas [...]

both Chevy and GMC pickups seem to be the same. What is the difference between a Chevy Colorado and GMC Canyon? What is the difference between a Chevy full size pickup such as a 1500 and a GMC? Aren't GMC pickups and Chevy pickups the same?