Silver, most of the drilled and slotted rotors here start with Centric Premium rotors, then are CNC milled and drilled at places like, Brake Performance. They don't cast their own.
That said, I would buy Centric rotors over most every brand.

Really do you know that for a fact? Regardless they still have a lifetime warenty on their slotted dimpled rotors for warping, cracking or any other defect. That is the best option in my book.

"Really do you know that for a fact?"
Well, Facts? Just what I read on the websites that sell the Drilled and Slotted rotors, and if you dig down into the fine print the e-coated or powder coated rotors start with Centric E-coated blanks. The CNC machines that drill them are in SO CAL.
My mechanic also tells me that there are only a few factories in the world that cast rotors.
Yes, from my experience there are a big difference in rotors.