what is the difference in brake rotors?

[John]

For an 04 WRX...I would suggest STI Brembos if you want a big upgrade.

And the reason a lot of shops wont turn drilled/slotted rotors is because it breaks the bits on the brake lathe

[fuji_production]

to add what bubba said drilled and/or slotted will and/or can be noisy. Nothing is better then oem or solid aftermarket rotors. unless your doing some serious racing there is no need to put extra or unnecessary stress on your pads/rotors...

[Kenny]

I would spend a few hundred dollars to find an aftermarket break kit with a solid disc and some mild performance pads. For a street car, never go overboard on the brakes. Spending $3k on a large brake kit isn't necessary. Spend the difference in upgrading the suspension, tires, and stainless steel brake lines.