The 250 6.7 are the new 7.3 from what I hear. My sister in law father has a 15' f250 and likes it a lot. In the 6.7 range there is the 11-14, 15-16, and looks like the 17' is a little different. They changed a few things on the 15' for the better. They have insta heat glow plugs so they turn over fast and real quite.
Now the 17' have all kinda cool things. Higher payload, fully boxed frame, rear door opens more than 90 degrees, and more power.