Thanks for all the great comments and please keep them coming.
Both of the 2007 trucks have 3.73 rears so they are both very similar from a capability point of view. The GVWR is an issue, though with the Quadcab long box being 12,200 lbs and the Megacab being 10,500 lbs. This does not make any sense to me; why did Dodge do this?
I also agree with the comments on the price; although they are both in great condition with relatively low mileage and are sought after, $40k seems like a lot of money for a 7 year old truck.