From my understanding, any braking is mainly based on the surface area between the pads and disks. So, all other things equal, drilled/grooved disks may increase braking distance due to the smaller area available.
The point behind drilling/grooving disks is tio dissipate heat quicker for the next time you are braking hard. This may prevent brake fade over successive braking zones if braking frequently (eg track driving or Stelvio Pass).
But, as ever, I may be wrong.