There are several differences that can factor into your decision making. The smaller diameter wheel will help the gearing ratio for making hill climbing easier but will limit the top speed that you are able to achieve. The larger wheel will make climbing hills a little tougher than the small wheel, but will make it easier to achieve and maintain a higher top speed. The longer spokes of the wheel will also absorb some of the vibrations of the road, making the ride a bit smoother. Tread wear will also last longer on a larger wheel.