The beam of light created by fog lights is usually wide and flat pattern; flat to stay close the road surface and minimize reflection back by fog - and wide to better illuminate the sides of the roadway (guard rails, curbs, lines painted on the roadway, etc.). Driving lights are usually merely bright spot lights designed to pierce the night darkness further than regular headlights. While fog lights are best for foggy conditions, either type of light will likely perform better than headlights due to their low mounting point on the vehicle. Experiment using all combinations (if possible) of fog / driving lights "on" and the low beam headlights "on" or "off" to determine which setting provides the best forward visibility for the driver. Do not shut off the running or "parking" lights, as they help make your vehicle more visible to other drivers alongside and behind your vehicle.
