That's the 11" rotor kit. What you'll get over the OE brakes is about 10 pounds per side weight reduction, which is huge for unsprung weight. The Wilwood rotor is thicker than the OE rotor, so it can absorb more heat, and the rotor vanes flow more air, so it'll cool faster. Compared to OE, you'll be able to stop just as hard but more often. However, with just a 0.25" increase in rotor diameter, stopping distances with the same type of pad won't be reduced much. BUT, the higher heat capacity and ability to dissipate more heat than the stock system means you can use a pad with more bite.
I have the now out-of-production 140-2508 kit, which had a stock diameter 10.75" rotor. It stopped about as well as the OE brakes.
But it didn't fade out during 20 minute sessions at Putnam Park road course two weeks ago. I cooked the OE brakes during an autocross many moons ago, so the Wilwood system's heat capacity is far greater. The pads also wore evenly almost down to the backing plates. The OE brake rotors will cone and the single-piston OE floating calipers don't clamp evenly, so you end up with uneven pad wear. So the Wilwood kit can get more life out of a set of pads than the OE setup if driven hard.
My advice? If you don't race the car, you don't need the kit, unless you like the look. Sell it to somebody that can use it.
If you do race the car, install the kit.
Or just install it. It's your car, you bought the parts. There's no downside to putting them on.
However, if you do race the car, the BP-10 compound pads that came with that kit aren't going to cut it. You'll want to step up to something like the Hawk DTC-30 or an EBC Yellow. If you're just streeting it, the BP-10s will be fine.