2WD or 4WD really comes down to personal preference. Do you get a fair amount of snow during the winter? Are you going to drive the truck in winter? Going to places in winter where there's snow? Then yes to a 4WD. Otherwise a 2WD will do. Only times a 2WD will fall short is where you are going and have to negotiate areas that are wet/slippery or when backing up a steep incline like AP said where a low range will aid you. Just depends on what/where you want truck to go/do.
Living here in CNY and pulling a snowmobile trailer, a 4WD is a must. Though I have seen a some (few) 2WD trucks towing sled trailers. Most trucks in my area are 4WD. MPG wise, she gets decent mpg's given it's weight and size. Not saying they don't require maintenance, but can be pricey when they do need repair.