IMHO, the only real choice in this scenario is to go with a diesel. Gasoline costs more per gallon while getting fewer miles per gallon, and it doesn't look like fuel is going to get much cheaper any time soon. In addition, while diesel has gone up in price, the price is not as volitile as that of gas. I have noticed pretty much that if gas rises a nickel, diesel rises a penny. And with today's modern diesel engines, there is not a significant difference in the maintenance cost between the diesel and a big V-8 or V-10.
As for which truck to choose, I think the Chevy or GMC would be the best choice if not for anything else except the Allison transmission. GM ran a series of magazine ads where they placed the same part from all three automatic trannies side by side like gears, shafts, bearings, etc. The pieces from the Allison made what came from the Dodge and Ford transmissions look like toys. All three motors right now are within a few points of each other as far as power produced.
One last bit - for regularly towing 10k lbs, I personally would move up to a one-ton (3500) series truck just for the dual rear wheels.
Cheers - Jonathan