I would go with the GM. The Fords seem to have better fit and finish and overall build quality, however the GM's tend to get better gas mileage, respond better to modifications, and overall better reliability and performance imo. The 99-07classic GM trucks (GMT-800) seem to be of better overall build quality than their '07 and up (GMT-900) trucks from my body shop experience. They have a lot more quality issues, but offer better powertrains.