Having driven a 3.7 at altitude...if you plan on passing through the Rockies, get the Ecoboost.
Never heard much on the powerstroke options in these. Wasn't it an inline 5? With diesel prices these days, might find a sweet deal on one.
i live right next to the Rockies and drive many passes every month. the 3.7 does it very well on a 10 000lbs vehicle. yes... you dont go up the pass at 70mph... but there is no issue going up, taking your time and hanging out with the 18 wheelers. I m never in a hurry with a full house on wheels.
if you want to race uphill.... ecoboost is insane and fun
if you enjoy life in the slow lane... the 3.7 or 3.5NA are perfectly fine and will do the job no problem.