The one with the 3.73 gears - better going up grades, better for passing slow trucks, better acceleration for merging with traffic. And be sure to get the factory heavy duty trailer towing package.
It is amusing to someone thinks you should spend an extra $11,000 of your money to get the 2015 truck. When it comes time to sell the 2015 you will not get any of that $11,000 back in terms of the resale value.
I work for my money and don't like to throw it around. I bought a new 2011 truck late in 2011 for under $42,000 that had I bought the new 2012 would have cost me over $57,000 for the same exact configuration. Only an idiot or a Wallstreet bankster using other people's money would have bought the 2012 truck. instead.