cross drilled/slotted rotors dont help you brake faster, they only help you brake repeatedly without overheating. They dissapate heat better hence you can slam your brakes more without losing distance.
No, that's not true at all. The idea is that the cross drilling helps the gas, created by your pads vaporizing, escape without building a pressure buffer between the pad and rotor. Most pads now-a-days don't suffer from this problem as much as they did when the technology was invented. The single greatest factor in how well your rotors help the brake system stop, is how much rotational energy they can convert to, and store as, heat. Look at Nascar rotors, they can hold so much heat that even when glowing red, the car is able to stop, and stop fast. Yes, the pads and calipers are part of it, but if we're talking about just the rotors, then it's how much heat they can store, and how fast they can absorb it. The cross-drilling and venting is more for looks now, than anything else.