Ok, here'* my thoughts in a nutshell:

1. Crossdriling is for cooling in EXTREME braking applications where you toss your rotors at the end of the race. It'* a tradeoff. You get more rapid cooling between braking cycles, but you sacrifice surface area of effective pad surface contact.

In other words, it'* not an effective street-use application. They are more prone to failure, and when they fail, they fail in pieces. This can cause major damage when it happens.

2. I'm a firm believer in the slot designs that go all the way through the outer edge of the rotor. Non-relieved slots like those won't discharge pad material or pad gasses (or even rain water) as well as slots relieved all the way to the ege. HOWEVER, in that case, it'* much better to machine the slot BEFORE hardening to relieve the natural stress points. Slots are chamfered so there aren't 90° intersection points with the face of the rotor on either plane (rotor face or slot bottom).

Rotors are also one of this things that 'you get what you pay for'. I wouldn't touch those if my life depended on it, and it does.

so why Auto makers put crossdrilled rotors on right from the assembly line they do nothing and are going to fail?? hey i doubt it the i know alot of research goes into the product before they even consider putting them on

The vast majority of those are either:

A) Cast holes in the blanks, then hardened.

or

B) Increased diameter of the rotors to make up for the surface area lost.

or

C) probably both A and B.

If you buy option A for your car, do option B to back it up.

so buy something high quality
BTW casted holes in the forgings make it alot easyier to work with thats if the foundry who supplys them make them accordiing to the print