Generally speaking, if all other variables are equal, the larger the wheel, the more roll you will get for the least amount of effort. So, you will be able to cover more surface area (distance) with the larger wheel with less effort. You will also go faster for the same amount of effort. And, due to the larger diameter, you will also get a smoother ride. So why use a smaller wheel size? Manueverabilty and precision.

Average quad roller skate speed wheels come in 62mm sizes, while artistic and rhythm quad roller skate wheels come in both 57mm and 62mm sizes. Also, be aware that some makes/models may have slightly different sizes (such as 58mm or 63mm).

One more thing... outdoor wheels can be found in larger sizes (65mm, 70mm, etc.) as the larger diameter will help minimize the affects of road imperfections.