Get the 5.7....I had a 2008 4.7 with the 310hp. I then traded it in for a 2010 5.7 and the difference is more than apparent. The torque is evident. Also, the Hemi is rated 1 mpg better than the 4.7 FYI.............

 

I just bought a 2011 SLT Big Horn. The incentives Chrysler are throwing at the truck are incredible just to move them. Truck sales are very slow. The 2012's are coming in with a 6 speed 'box so any dealer with '11 inventory is going to blow these trucks out the door. I got my $43k truck for >20% off sticker. You just need to haggle a little.
Don't buy the 6 cylinder... unless its the new F150 Eco boost, because you will be sorry.
Good luck.

 

As an FYI i get better gas mileage with my 2011 Ram 5.7 than I did with my 2007 4.7 HO Dakota. On the highway i get between 20 and 18 in the Ram the Dakota i was lucky to get 18

 

Wow, a 6 speed auto on the hemi sounds really interesting. Will they be putting that on the pentastar V6 too? It should improve fuel economy a bit over the current 5 speed setup.