I have the Chevy 6 liter gas, 2012 model. I chose the gas version because I just don't tow enough now, to justify the additional costs to purchase the diesel, and maintain it. They are ten grand more, but that's not the ? you asked.
I wanted the GMC as I had a 2500 Yukon XL previously. When I needed a truck, there simply weren't that many gas GMC 2500's on the market. I found this Chevy in NJ, it was certified pre-owned with only 9k miles on it. I saved a bunch, and got the full factory warranty.
Pros: Sits 2" higher than a 1500
. Brakes are massive, and boy do they stop this truck. 6 Liter is a proven block, with parts readily available even in the boonies. 300 HP's under the hood. When you need 'em, they are there. 36 1/2 gallon fuel tank. A long way before your next fillup. Frame is huge, and lots of room under the hood. Tows almost anything I can throw at it with ease. Roomy cab. I got the rear DVD, and whoever is in the back can watch a movie, while I listen to XM.
Ride is smooth as silk when towing, and rides better with a load.
Cons: Can be tough to park, even when I chose the 6 1/2 foot bed. I couldn't imagine the 8' bed. A little stiff w/o a load. Don't like the electronics as they were outdated before they even built the vehicle. Leather seats are only partially leather. No bluetooth. Options are WAY overpriced if you buy new. Even tho I have the 3.73 rear end, I feel I should get better gas mileage. No inside handle grips directly above your shoulder. Only at the 2 o'clock mark when seated. Good for entry, worthless for riding. Far too stripped of a vehicle for what you pay. I have SO many upgrades in mine. From window tinting, rear under-seat storage, bed liner & a rubber mat, LED's. For what GMC charges, you should be getting MANY more options on the vehicle.
New, these damn things are now over 50k. With the GMC's in the 60k $ range.
Ridiculous. It's GMC's cash cow, along with their Yukon XL & Denali. Too bad they KNOW this. Sorry, I am a working man paying for three children's college edumacation. My wallet is only so deep. Yes, I am happy with my truck, but I don't like the price I had to pay. If you go with the 2500, make sure you get the 3.73 rear end. The new Cheby's have the 6 speed tranny. My old Yukon did not. If I went much over 65mph in the Yukon, the fuel consumption wasn't worth the 2 extra minutes to get there. Definitely buy used, and preferably re-certified Let someone else take the HUGE hit when THEY drove it off the lot, not you. It does the towing job very well. If you get hit in it, with the size of the frame, THEY are gonna be hurting, not you. I do like the safety factor of the larger & heavier vehicle. My family's safety is worth the extra fuel I pay to own it. It's a beast, but that's what you bhought it for, is to do beastly things. And it does those very well IMHO. Good luck, stay safe, and enjoy the ADVENTURE of owning your AS.