Dimpled not drilled from my experience.
I've been running slotted and dimpled on my 08 for almost 40k now. I installed stainless lines at the same time so I can't say one or the other contributed to the better braking feel.
I've been running Powerslot rotors on my Ex for more than three yeas now. They still have an excellent surface and no signs of cracks or crazing. I liked them so much that I went with the cryo-stabilized versions on my 450.