Brake rotors are the heat sink of your 2004-2005 WRX's braking system — their job is to absorb and shed the heat generated in every stop. Upgrading rotors makes sense when the factory units are cracking, warping, or simply cannot keep up with track temperatures.
Rotor face design is the main choice. Blank (smooth) rotors offer the most surface area and longest life — the right pick for street cars and many track cars. Slotted rotors help wipe the pad surface clean and evacuate gases under hard use, at the cost of slightly faster pad wear. Drilled rotors look racy but are prone to cracking under track heat; modern pad compounds do not need the holes.
Construction matters for tracked cars: two-piece rotors with an aluminum hat save significant unsprung weight and resist warping through heat cycles far better than one-piece cast rotors. For street use, a quality one-piece rotor is entirely sufficient and much cheaper.
Always replace rotors in axle pairs and bed new pads to new rotors. Verify the rotor diameter and hat offset match your calipers — especially with aftermarket big brake kits. Filter by rotor surface type and construction for your 2004-2005 WRX.
Measure rotor thickness before deciding to resurface versus replace: most WRX rotors are inexpensive enough that replacement beats machining, and a rotor near minimum thickness has less thermal mass — which is exactly what causes the fade you are trying to fix. When in doubt, replace.