Sadly, many guys that buy new trucks don't know shit from apple butter about what they are getting. Often the extent of their decision making is going to the dealer and saying: "I'll take the red one with the big wheels!" A truck that is highly geared-ie 3.08 for instance-will lope along easily on level ground at low rpm and get the best possible mileage. But put a trailer behind it and cross a mountain pass and you will think about 1/2 of your horsepower is missing. It's all in the gearing, the wrong axle ratio can make towing a nightmare in hilly terrain. Your truck may be just fine in Kansas or Nebraska but struggle like hell to tow in the mountain west.
When I ordered my truck in 2014 had I taken the standard rear axle my towing capacity would have been 4,450#, not much for a full sized truck. But by checking the box that said "3.55 rear axle" my towing capacity went from 4,450 to 7,300 pounds. A nearly 3,000 pound increase for $43! And the peace of mind to know that it can sail over any mountain pass without making me think I need a V-8. V-8's are history now as several manufacturers have dropped them altogether in favor of the more efficient turbo V-6. In-line 6 cylinder engines are making a comeback also and seem to offer better torque characteristics than a V-6. They are smooth running engines. And to show that the V-8 is on it's death bed, Chevrolet is now selling a full size Silverado with a turbo 4 engine.
Know what you are getting-don't buy a rig that is geared for the prairie to drive across the Cascades or Sierra. You won't be happy if you intend to tow.