If you have your mind set on skipping past the full-size Silverado (or F-150 or Ram 1500, for that matter) and heading for the somewhat more manageable 2016 Chevrolet Colorado—or the closely related GMC Canyon—you’ll be facing a dilemma: do you get the V-6 gasoline engine, or the new-for-2016 Duramax 2.8-liter turbo-diesel…