I'll bring the cost equation. SRF, IMO, is like longer lasting Motul. Since I bleed my own brakes, I use Motul. If I paid someone, I would put in SRF and leave it for a year.
OEM brakes do not meet 3 of the 5 criteria you listed (easy pad changes, pad selection, last for 20-30 minute HPDE session). No one NEEDS a BBK. Just like everything else on the car, it is the responsibility of you, the driver, to manage its shortcomings.
If you are going to keep the car and drive it on the track regularly, a BBK can save you money, gray hairs, and frustration over the long run.
Originally Posted by JAJ
Your Stoptech's are not set up properly. Any quality BBK will provide better pedal modulation than stock, and I agree stock is very good on the M3. So if you've got pedal drop and grabbing with Stoptech's, then something's wrong.
Brake pads make a big difference. The ST performance pads do OK but they will glaze when you overheat them and then they will have zero stopping power. Just like any other pad that is not designed for high temperature operation. High temp pads work differently since they grab and "stick" to the rotor where a street pad relies on friction and pressure.
My STs are much less grabby than the OE brakes which were like on/off switches with track pads.