Sides of the foundation.
Do you get snow?
Rule of thumb I've used is presume you park a car in front of each door. If you get out on the car on the lawn side of the driveway, what do you put your feet on? Concrete or grass? If grass and you let any amount of snow, you're getting in and out in the snow. No snow? Then you're getting in and out on the wet grass.
If you're fine dealing with the wet grass or snow ... then narrow. If not, widen it out until you're happy with what you stand on when you get out of the car. Don't forget you'll want to probably swing the door further than where you stand.
