Cross-drilled rotors look fast and are marketed as an upgrade, but do the holes actually help your braking? For most drivers the honest answer is: not much. Here is what drilled rotors really do.
What the holes are meant to do
The drilled holes were originally designed to vent the gases and dust that old brake pads released under heat, and to channel away water, giving the pad a cleaner bite; see drilled vs slotted rotors. Modern pads out-gas far less, so this benefit is smaller than it used to be. The holes also shed a little weight and look sporty.
The downside: cracking
The holes create stress points, and under hard, repeated heat cycling drilled rotors can crack from hole to hole - see do drilled rotors crack. This is why many track drivers actually avoid cheap drilled rotors and prefer slotted or plain. Drilling also reduces the friction surface area slightly.
Slotted is often the better upgrade
For performance use, slotted rotors give many of the gas/water-clearing benefits without the crack risk of drilling - see slotted rotor benefits. Slots wipe the pad surface and vent gases while keeping the rotor structurally stronger.
Do you need them?
For normal street driving, a quality plain or slotted rotor is all you need - drilled rotors mostly buy looks; see do bigger brakes stop faster for the general point that grip and pads matter more than fancy rotors. If you like the look, buy quality drilled rotors, but for function pair good pads with the right rotor and fresh hardware.