Well, we'll see how long this thread goes for before it gets shut down....
I picked the truck I did primarily for the powertrain. The Cummins engine is tried and true and is the least complex out of the 3 diesels available. Have a look under the hood of all 3 and think about what the long term cost of ownership will be if and when repairs are required. The Ram/Cummins is far simpler and less cluttered under the hood than the V8 diesels offered by GM and Ford which should make long term ownership cheaper. A huge advantage of the Ram is the fact that it uses the Bosch CP3 fuel injection pump which has proven to be much more reliable than the CP4 pump that is used in both the Ford and GM. Failure of the CP4 pumps ruins the entire fuel system and costs between $10-$15k to repair, which was a risk I simply was not willing to take. I also like the manual transmission only offered by Ram because I believe that will also be less expensive in the long run. Now that I have had this truck for a few months and towed quite extensively with it, I absolutely love it. The Cummins has massive low end torque and the exhaust brake is fantastic in the long and steep mountain passes we have here in BC.
The other reason I picked the Ram is for the truck itself. I believe that the 4th generation (current generation) Ram is the best looking truck out there, especially in a dually. The interior is also much better than in the past, and they were improved again in 2013. I believe that Ram used to be lacking in interior and comfort features but definitely no longer. They have all the bells and whistles the others do and the cab is very comfortable, functional, and attractive. The noise in the cab is also very low even when the truck is working hard. Ram also redesigned the 3500 truck in 2013 and now have a GVWR of 14,000 lbs and available tow rating of almost 30,000 lbs when equipped with the Aisin transmission and 4.10 rear axle. I would not hesitate to tow a 18k lbs fifth wheel with my truck at all; in fact we are currently looking for a larger fifth wheel that will likely weigh somewhere around 16k lbs.
I have owned 3 Fords over the last 20 years including both a 7.3L and 6.0L diesel. I got tired of the constant little "issues" with these trucks and the resale value on the 6.0L was terrible. I plan on keeping my current truck for a very long time (20 years) so I wanted the most reliable truck available. To this point I have absolutely no regrets in my decision and believe I made the right one. My wife also loves this truck and drives it as well.