When you need to stop right the fuck now in a modern sporty car, what's limiting you: Your brakes, or your tires?

The line that I subscribe to is that upgrading the brakes on your sporty car in the aim of shortening braking distance is almost entirely pointless for road use, since no matter how hard your brakes can slow your wheels, it's ultimately the friction between the tire and the road that stops the car. So unless you can't engage ABS or it requires uncomfortable pressure to do so, upgrading your brakes won't help.

However, others insist that big brake kits and the like are absolutely essential because, to quote one member of Audizine, "If you don't understand why then you shouldn't even be on this forum." This was after I presented a detailed explanation of the physics involved in stopping a car and asked him politely what part of that was incorrect.

Granted, I completely understand things like braided lines, or even different brake things to improve the brake FEEL, but this was specifically about stopping distance. I also understand that if you're on a track, or an idiot on the road, upgraded brakes do a much better job of resisting fade. That said, even on white-knuckle, don't-actually-remember-what-happened canyon blasts in my S4 (with the same brakes as the A4, which started the above argument), I have never felt like my brakes faded. They're starting to feel a bit spongy with age, so I may look into braided lines just for pedal feel, but the car can still choke me to death with the seatbelt and make all sorts of chirpy noises even on Michelin Pilot Super Sport tires. I even have the computer tweaked so that my brake lights go into rave mode.

That said, I'm open to the idea that I've got something wrong, provided someone can provide a rational explanation besides "It just does, shut up!"