if anything they make the pad last longer. they do have more bite which increases wear but the groove also assists in cleaning the brake dust off the pad and venting it out so its not actually trapped between the rotor and the pad, and that itself helps the pad to stay alive a bit longer...
You'll still have benefits with cross drilled however many cross drilled rotors are prone to stress fractures due to the fact that they are drilled after the rotor is forged, whereas the slots are actually shaped within the forging/casting process. You'll notice RDA also have the gold passivated rotors with slots and 'dimples'. The dimples are done during casting and dont go the entire way thru the disc, so theyre much hardier. cross drilling isnt so useful for street work (lets face it, its there for cooling so its mainly for racers)... slotted is more than enough for any street car.. if your slotted rotors aren't doing the job on the street, then thats the time you consider caliper and disc diameter upgrades... or switch to a prius
I've already added a cusco brake cylinder brace and braided brake lines and those two improve the feeling/response of the brakes quite a bit. The new rotors should really seal the deal, I can't see myself needing bigger calipers or disc diameter...
-D