The Z's stock calipers are just plain vented meaning that they just guide air through the inner section of the rotor. The high performance rotors (and Skyline rotors) are axially vented meaning that they 'scoop' air through the rotor. Crossdrilling is just crossdrilling.
John Yim (Houston) 91 ZTT Stage...stages are confusing. Just read the mods. :) 30 BP, Houston Region SCCA "...Just as they're about to catch me... Twin... Turbos... Kick... In..."