folk dont moan about it because folk dont really understand the implications.
Imagine your brakes are perfectly balanced, and you brake hard, at the point of maximum decelleration before the wheels lock.
The cars weight gets transferred forward, which means you can brake harder on the front wheels than the rear. All the calipers are fed with the same hydraulic pressure, so the rear ones need to apply less force for that given pressure, hence they have smaller pistons and , so the front calipers are larger (and the disks too) to compensate.
However the limiting factor is infact the tyres grip on the road surface. If you brake harder in the above scenario in your perfectly balanced car, you lock the wheels, ABS engages, everything goes to ****. If everythings perfectly balanced, all four wheels are applying their maximum decelleration to the road.
So folk fit larger brakes. say you go from the 288's to 345mm S4 fronts, and lets imagine those brakes are 30% stronger for a given hydraulic pressure. So the first impression is the brakes are "better" because you dont need to press the pedal as hard (or conversely, stop better for the same pedal effort).
However theres a caveat. To get to the same point as above, where the front wheels are about to lock, you dont have to press the pedal as hard, because the brakes are more powerful, but the tyres are the same. This seems like a good idea. However what you then end up with is the front wheels about to lock, and the rear wheels only putting about 70% of their maximum available braking, because the line pressure is lower.
Thus the total force applied to the road surface drops in maximum effort stopping situations.
All cars are biased to the front from the factory, because its safer, so you've got a bit of leeway, but fitting 345mm fronts and leaving the stock rears is almost certainly going to reduce your maximum stopping effort.
