Holes/Slots: Sometimes, the pads can get hot enough to where they start giving of a gas. This gas gets between the pad and rotor and acts like a lubricant. The holes/slots give some place for the gas to escape. Also, the holes/slots are always scraping the pads, giving you a fresh pad surface for braking. Holes also help with cooling. Great for people with lots of money and that do serious racing where the improved braking performance is wroth the money.Its better the blanks rotors than the drilled / slotted?
Blanks: More surface contact for better friction. Cheaper. Longer lasting. Don't have the potential for forming cracks around holes. Perfect for DD and weekend warriors on a budget.