Automatic, I drive mostly city empty as my truck is my daily driver and I do not go on the highway to get to work, the auto works great.
I just got back from a 700 mile trip towing my 5th wheel, I went up and back to Lake Placid, NY, worked great, not sure of the elevation but it is alot of climbing. All I needed to do was turn off OD and I handled the back roads up and downs at 55 mph, 2500 rpm with no problem, downhill as long as I was running faster than about 48 mph the TC stayed locked and did a pretty decent job of holding the truck back, the rest of the time, like when coming out of toll booths I just let it do it's thing and it worked perfect, 68 mph on the major highways with the cruise on. If you get an automatic be sure to get the 4. 10 gears they put the engine right at 2000 rpm at 65, I like to be slightly higher, about 2100 rpm which is 68 mph. Had fun passing the gas trucks towing on the hills, once they get into the elevation they really suffer.