The Speed you want to be able to skate should be a determining factor as to what skate to purchase.
Leisurely - Mellow cruising at slow to moderate speeds. Great for newer skaters or children.
Moderate - Skating at a variety of speeds, both mellow and fast. Good for more experienced skaters that will not always be skating at top speed, but will not always be cruising at mellow speeds.
Fast - Skating at moderate to fast speeds at all times, or for skaters that really like to push it, or enjoy a high amount of aerobic workouts.