Your usage is the key to your success.
And that's the truth. I live in the "endless mountains" region of Pennsylvania. None of our "mountains" are large compared to many places, but the good hills we have are one right after another (thank you glaciers). That said, our local dealerships often struggle with how hard it is for them to get in the manual transmission vehicles that people want in this area, as around here, auto tranny's are often up for failure.
However, a good reason for that failure is not the auto trans itself, but they way it is used. With higher fuel economies so many vehicles have a final drive ratio that is so slow running a vehicle in "Drive" (what used to be listed as overdrive) means the poor trans is shifting all the damn time. I'm willing to bet that if people just dropped it down a gear for their driving in a region like this and reserved the top gear in an auto for the interstate, that a good many of the trans problems could be eliminated.
For me, I'm a bit of an OCD type and record the fuel mileage for every fill up. W/ my last auto truck, it made NO difference in fuel mileage doing my normal driving on these hills consisting of 25mph, 35mph and 45mph roads whether I was in Drive or 3rd gear. That said, I kept the thing in 3rd and did the tranny a favor unless I had to take a drive on the interstate.
The problem with buying a used vehicle is that you don't know what they did in terms of daily operation and / or maintenance in many cases. Sometimes you are lucky (as I was buying my last vehicle in having a ridiculously meticulous service record from the dealership come with it which is why I bought it versus a newer used vehicle) but usually it's a guessing game, which is for me, doing my own service work (including clutches) that I often pick a manual trans over an auto when buying used.
At the end of the day, whether you buy a truck or a van, settle on whatever gives you the best value for your dollar based on your visual analysis of the vehicle and the things you can prove have been done or still are right with the vehicle.
I sold my 04 colorado and was looking for an 04 or newer SUV to replace it with. I wound up with an 01 xterra because I had never seen a service history so complete in my life, the vehicle was 9 years old and traded at the Nissan dealership which told me after owning that they wanted another Nissan, and I knew they wanted to sell it because in 500 miles it was due for a 900 dollar timing belt service which I did myself for about 200 bucks. They were so meticulous that if they kept it, they would have had the job done but decided to spend that on the new vehicle instead. There was nothing wrong with that truck and (knock on wood) in the last 30k miles hasn't given me a bit of a problem, which is much better than I can say for the vehicle I have under warranty yet.
pen