Can't go wrong with PPG, although Van Sickle and Valspar tractor/truck paints are very good, too. I've also heard good things about the Dupli-Color pre-mix paints from the parts stroes, but the color selection seems limited, or at least in my area they are.
As to DuPont, never had good luck with DuPont. Doesn't seem to want to stay on the vehicle. Both my Blazer and my Dad's '88 Silverado have DuPont on them, and both are either peeling or flaking off.
