I've heard it like this. Chevy is for all the guys hard working on the day shift, GMC is for there supervisor. Does about the same job but for a little more lettuce. Don't get me wrong tho, I love GMC just as much as I do Chevy, I wouldn't hesitate it get a GMC cuz it's "not a Chevy".
My girlfriends family drives all GMC and my family is all Chevy. So I don't have to worry about her calling me to come rescue her ford died or Honda quit working haha.
GMC is a little more expense yes, but if I was looking at 2 identical in every way trucks, except the name plates, I wouldn't know which to choose.