Where will you be using your skates?
Will you be skating inside or outside? (This means what type of surface will you be skating on)
concrete (some rinks)
wood floor (rink)
trail skating (which could also be concrete or asphalt with the occasional debris i.e., tree limbs pine cones
What type of skating will you be doing?
Typically this style of skating is what you would see while watching ice skating competitions.
This style of skating is kind of self-explanatory. Imagine watching the Olympic speed skate competition, now imagine the skater in a pair of quad skates.
Jam skaters share some of the qualities of a speed/artistic skater. A Jam skater values speed as well as quick movements. When you think of Jam skating think of "Soul Train" (for those who don't know what soul train is, it's a dance show that aired in the early 70s hosted by Don Cornelius.)
Roller derby is an aggressive form of skating. Derby is a skating sport, so these skaters favor speed and maneuverability.
What's the deal with indoor wheels?
Indoor wheels are hard, enabling the skater to glide across indoor surfaces i.e., the skating rink.
The durometer of a wheel is the hardness of a wheel. The durometer of a wheel is measured from 0 to 100. Anything 90A (The letter A after the number means the wheels are made of Urethane) and above is considered an indoor wheel. The higher the number the harder the wheel the less grip you will have ( Imagine you're rock climbing. You reach up to grab a rock, but there really isn't enough rock to grip, so your hand slips, and you lose your balance, but luckily you catch yourself, this is a good way to describe the feel of an indoor wheel.)
What's the deal with outdoor wheels?
Outdoor wheels are softer to absorb shock while cruising outside. This means again, debris i.e., sticks, pine cones, and rocks. Any Durometer below 90A is considered an outdoor wheel.
What about wheel size
Great Question, what about the size?
The size of the wheel does matter. The smaller the wheels the more maneuverability, but smaller wheels are slower. It will take way more effort to attain and maintain speed. Were as larger wheels are faster, but the skater will be unable to perform quick agile movements. Larger wheels also prevent stability. The most common wheel sizes for quad skates are between 47 to 57 mm.
Take a look at the diagram below.