Brakes don't stop the car. The tires do. Brakes only convert kinetic energy into heat (unless you have KERS, then it converts energy back into stored energy, and this car does not have KERS).
Let's be clear on WHY they're awesome. I say that because my race car has 9.5" rotors and I do just fine. BUT, I do just fine because I have 1600 degree pads, 600 degree brake fluid and brake ducts.
So here's a list of big brake benefits but even if you track the car a lot I still argue that they're not *needed* regarding getting the job done, but they are nice and here's a couple reasons.
1: with big brakes, the rotor has a significantly larger surface area to dissipate heat and the larger disc acts also as a larger heat sink. This results in:
1a: The heat generated is the same but the temperature won't be as great as the heat is spread over a larger surface area putting less heat into moving parts: caliper sliders, ball joints, tie rod ends and wheel bearings.
1b: Braking heat is transfered into the hub and the bearing and with the larger rotor, the heat generated is spread over a larger mass, more heat is dissipated quicker and with the blades further away from the center... less heat is transferred to the hub and bearing.
2: With big brakes it allows a track junky to simply run an aggressive street pad meaning they won't need to swap out to "track only" pads for the event since the pads won't see crazy temps and they won't need to bleed their fluid as frequently.
Just to re-iterate, with proper fluid, pads and ducting the stock brakes will do what you need them to do even if you're a proper track junky, they just won't do it "conveniently" (cuz pads, fluid, ducting!
). Primo has the right mind for a brake upgrade considering his intended use.
I hope this helps.