As brake pad material is vaporized by the heat of intensive spirited driving it produces gasses that have to escape to reduce brake fade. Drilled and/or slotted rotors help to vent those gasses. For a plain Jane daily driver it will be hard to notice a difference. The brakes will feel better simply because new pads and rotors are present. Drilled/slotted can result in slightly shorter pad life because they wipe off pad material faster. That, too, is hard to quantify because so many cars with d/s rotors are driven and braked harder. My pickup warps OEM plain rotors in about 20k miles so I might try d/s because they don’t cost more and pads are a cheap half hour job, just to see what happens. If your friend drives hard and lives in mountain country, why not? For my old man flat land driving I don’t expect to notice better braking other than maybe better warp resistance but I have no proof of that. It is flat here, we can see a mile down the road, and we roll out to a stop and hardly use the brakes.