You're both coming from different directions, that happen to be correct.
On the street, slotted and/or cross drilled rotors hurt your braking performance because they don't allow the brakes the get to their optimum temperature. Slotted rotors will also decrease the life of your brake pads because they shave material every time the brakes are applied, by design. This is to prevent glazing under race conditions.
You can find Brembo blanks at
TireRack.com.com.