Fred, DM is right about the dually's on slick roads and in snow.....they suck!!! My buds 06 DM Dually is stuck in 4+ inches of snow. They do tow much better than SRW but everything else is worse. If you towed ALL of the time, then go with the dually. For sledder's, dually is definately a hinderance.
As for the trans (my language), the 68 RFE that Dodge came out with in 2007 is about 10,000 times better than the 48 RE in your 06. It seems like the only time I ever get to work on these newer generation transmissions (big 3), it is for upgrades (billet lid torque converters) or for electronic problems ie: speed sensors or reflashes. However, the Allison is just a little better and beefier than the Dodge 68 RFE and Ford's Torqueshift.
I'm asked for these truck rec's all of the time. I have actually recommended A: find your best price B: do you plan on lifting the truck? If so, then go with Ford or Dodge. If not, then go with GM.
I still like the GM best though.