BMW has faired poorly compared to merc and audis and even lexus in this department. even the 35s and Ms fair poorly in head to head tests. Ive tried BMW performance, Brembo GTs, 335 brakes, as well as previously ATE, EBC red, EBC green pads; my humble 2 cents.
EBC red/ EBC green with stock rotors and calipers: both gave huge improvements brake dust, wheels were relatively dust free even after 1-2 weeks without wash. But braking improvement was negligible, I always felt the response was too retarded and cant pull me to a stop in time. Its a cheap upgrade to keep the rims clean but almost helpless to braking characteristics.
ATE: marginally better brake bite, nevertheless I still felt that somehow I couldnt brake at will especially if im travelling at expressway speeds.
335 brakes: i started by changing just the front setup, the improvement was marginal, slightly better than stock, but somehow was disappointed by the entire braking characteristic. I'd have expected more of the 335s. I always ended up stopping very close to the car in front especially at traffic lights. So i took it one step further and went for the rear 335 brakes too. Immediately the difference was significant, the brakes bit way earlier and was less progressive. You could feel the car puling to a stop from speeds over 100kmph. It was impressive and very value for money, and is definitely good enough for day to day use if you drive in a civilized manner.
BMW performance: this felt similar to the 335 brakes, they however, had more brake dust, yet more bite especially at high speeds. The 335 brakes seem to be less predictable compared to Performance if travelling at NSHW above legal speeds. The 335 feel was not very linear especially if braking hard or before cornering in, its almost as if you get a different feel when u input different force on the brakes. On the other hand, performance brakes was smoother and more linear while giving more bite at the initial point when driver starts braking.
Brembo GT: these need no introduction. 6/4 brembo gt gives great control and the feel is hard to describe. Its best used when you cross the checkpoint and tear down the roads abusing what little ponies you have under your hood. The brakes are very predictable and easy to handle. Across all speed range, they are quick to react and yet dont kick in too abruptly. Its almost as if the brakes are able to compensate for your input. For example, if i doesnt matter if I brake with 20% force or 60% force, the braking feel is very linear and similar, and brings the car to a halt in a confident manner. They dont give you a characteristic sudden jerk that is typical of Jap cars like Lexus when you jam the brakes. At high speeds the brembos are massive when u perform an E-brake; the stopping force is dignified yet composed, it's able to stop the car in a short distance without jerking you off your seats (the brakes were nonetheless so efficient that I never remembered having to E-brake, usually 80% force is enough to brake in all circumstances). For the price though, these brakes are an overkill in SG roads and you end up getting quite pissed when cars in front of you brake miles before the red light. Such toys are better left for days when you need to unleash the inner beast.
Cheers