I drove the '08 Ford and '07 Dodge and none come close to the GMC. This is my second GM truck. I'm very hapy with it. The power is great. The only draw back is the mileage, but I was expecting that from a big truck.
Traded my 2006 Sierra 2500HD 6.0 V8 for the Allison/Duramax. Super truck. I was amazed how much better the ride is in the 2007 Sierra Classic. Duramax/Allison combo a real delight to tow with. The Allison 6 speed works incredibly well with the Duramax to couple all of that torque to the ground as well as assisting in stopping the whole load. Torque comes in at about 1500 RPMS and this thing launches like a rocket. Great fit and finish. I researched all other diesels and I'm happy I stuck with GMC.
This truck is a replacement for my stolen '03 F-250 Powerstroke. After 11 months of trying to like this truck, I would take my 4 year old Ford back in a heartbeat. The much-touted Allison tranny screams like a banshee when I am towing up the long steep mountain roads in NM and AZ. It's clunky and jerky. Trips to the dealership have found nothing wrong. The mileage runs around a dismal 13 mpg vs. 18+ for the '03 Ford. This heavy duty truck came with puny 6 ply road tires on it, which I think is ridiculous. I resent having to shell out for 10 ply Michelin all terrain tires at 6000 miles because the truck tires couldn't get a grip on our muddy winter roads, even in 4WD.