We cannot compare motor bike rotors to car rotors, cast for car & steel for the bikes.
Unfortunately some suppliers are just drilling cheap cast rotors and marketing as something special for more money. Slotted & drilled rotors look the part but on a street/cruiser are not needed unless the wow factor is what you want. Buy quality brake rotors, either types, what price can you put on safety and use quality pads. Best disc's rotors in the world and poor pads will be a problem.
Bike rotors cannot/shouldn't be machined (too thin), most car rotors can be machined or ground depending upon finished thickness.