4WD and 2WD will have no difference in the quickness of your car. What determines how fast your car goes is the cylinders and the horsepower. You can purchase the exact same car one with 4x4 and one that 2 wheel drive both V6 and they will go the exact same speed. Some things that you may want to look at is if you travel in the snow or mud often and if so you would want the 4WD or AWD, but if you live somewhere where you don't get snow or you don't like to go up in the mountains than a 2WD would do you just fine. One thing you must remember is that most trucks and suv's that are 2wd have rear wheel drive not front wheel drive which will make your car squirrelly if you do end up taking it up to the snow, or mud, or if you are driving in heavy rain with standing water. I personally wouldn't drive a GMC, but thats my opinion.