Every little thing helps so go with the full face. Mine saved me a ton of pain when the truck in front of me kicked up a stone the size of a quarter. The stone hit my sheild and took a chunk out of it .25" across, right at eye level. A new sheild cost $15 and as far as I know, there is no way for me to get a new eye. Beyond the helmet, I wear armored gloves, leather jacket & pants when I am out.
When your drive/ride in a car you have seat belts, air bags and a steel frame around you. With a bike, you have none of that. Stay safe, stay protected and stay upright.