I prefer the 3rd gen 1500's over the 4th. I am not really one that cares for luxery and all the fancy built in options.. Don't need heated seats and seperate climate control and such. I love being able to stand on my bumper and in my engine bay at 6'3. I will also take leaf strips over rear coils any day. As I work for my dad's RV dealership and my trucks hauls every once in a while and we always get customers with 4th gens... The suspension between 3rd and 4th makes a huge difference in hauling.
But we just bought a2013 Cummins 3500 Dually coming in this week to relieve our 04 2500 Hemi and 08 F350 and my truck.
For 2500--- For sure the 4th gens, and for 3500 duellies I could go eithor 3rd or 4th gen.
Brandon...Check out my build thread here