Fit some super sticky tyres to the 1.8 A4 on stock brakes and it will stop faster than an RS4 on plastic-fantastics, might only manage it once, before overheating the things, but it will stop faster.
I know what you mean but it is not as simple as that.
if you are making the ABS cut in the brakes are not working at their optimum. its the ability for the pad to scrub off as much speed as possible WITHOUT them locking up or having the ABS cut in that counts.
you learn pretty quickly where the lock up point is and you avoid it for a reason.
there is far more modulation in a larger rotor and you can get closer to the point where the wheel locks up and hold it there. the fact that the rotational energy is only turned into heat gives you only one exit for it, through the metal mass itself. increase the ability for the system to lose heat from braking and it is as significant in the single application of the brakes as it is in a track situation where you boil you fluid.
I doubt very much stock 1.8t brakes with same tyres would manage to pull up once faster than an RS4 on **** tyres unless they were so bad they were illegal.
basing this on personal experience of 1.8t brakes vs RS4 brakes on the same car with same tyres. all weights and forces are pretty much exactly the same.
hauling my 1.8t up from 90mph on stock brakes was a scary occurance. they regurlarly lost braking power on a single long application from high speed. I can think of one shorter than average motorway slip road exit with a roundabout at the top that sticks in my mind and my trousers, where from about half way through the pull up there is no way in hell the brakes would be able to lock up the wheels. they were barely doing anything!
This was not brake fade due to heat build up from lots of use on a track day but from one press.
same tyres, fitted temporarily to new wheels, running 8 pot brembos and EBC yellow pads not only was the ability to pull up improved dramatically but so was the lack of fade.
now with new tyres they are night and day.
I don't notice the ability to lock up the brakes more than before, I am not constantly slamming into the steering wheel as you obviously get used to the new set up.
but they are without doubt better at pulling the same car up on the same tyres.