That's sort of comparing apples to oranges. You have an 05 duramax without any emissions equipment to worry about. I would consider keeping the RAM if deleting was an option, but my guy who does my annual safeties just cant let the deletes slide anymore. I agree with you completely, i have a 2007 5.9 cummins welding rig that has 220,000 miles on it and still running like a beast. But of course that's with no emissions equipment.
Theres also a lot to say about driving a truck with full warrenty... i have good experience with both... paying for repairs on my welding rig is expensive enough with the 24v 5.9, couldn't imagine paying for some items on this 6.7 RAM. Piece of mind has its own cost for sure.