Just wanted to chime in and say how great my truck is. Ok, only six months old but no regrets going for brand new vs pre duonic transmission. My wife and I are in the fortunate position that we have enough time on our hands that should something go wrong, which it hasn't yet, we can wait for it to be fixed. Because everything can be fixed. I have driven a Land Rover for the last 16 years, so believe me, I know a thing or two about the statement, "everything can be fixed".
Seriously my new truck is a delight to drive. I smile every time I get into it. Sure, I would would probably enjoy an older model just as much. I would add that all of the EC owners I have spoken to, truck reliability issues is not the first thing they bring up, regardless of the age of the truck. New or old, I think they are both viable choices based on your own personal criteria. I am happy to have DEF as I am putting less crap into our environment. If you plan to go to South America, pre-DEF probably makes sense.