In my opinion, Killer Bees are fine, but not great. Cleaning is not worth the work, and they're never as good as new. A good blader does however own bearing cleaner and lubricant. The wheel diameter in millimeters, and the hardness rating. Different wheel brands and formulations feel different even at the same durometer rating.
Wheel diameter is discussed above.
I feel that durometer ratings of 74 or below wear out too fast, but may give better traction on a wooden floor for example. Ratings of 82 and above are hard to find except in the tiny aggressive wheels. I have tried 86 and found them very strange, like solid plastic. I bought my first blades in 1994, inspired by an ex-girlfriend. My current is RollerBlade Aeroblade purchased in 1996.