The basic theory here is the bigger the wheel, the faster you will go. But there is a weight trade off. The bigger the wheel, the heavier the skateboard. Wheels also have a width size that is not usually specified on the wheel. Again weight factor comes into play here.
Wider wheels tend to have more grip, as opposed to thinner wheels.
Also, you want to have wheels that fit the board correctly. Smaller boards need smaller wheels and vice versa. 87A - Cruiser riding, long boards, hill riding. Very rough surfaces. 95A - Street riding, rough surfaces, smooth, fast, and durable.