These are excellent questions, and really show how the marketing of some BBKs can be confusing.
First, let's get this out of the way: do not expect a BBK to give you shorter stopping distances. That is not the purpose at all.
The benefits of a big brake kit include much greater heat absorption and dissipation capability due to larger heat sink areas of pad and rotor, better repeatability of performance and resistance to fade due to this greater heat capacity (known as
heat management), better pedal feel and modulation, and more durable component life. With some systems, you're even reducing weight... even with larger rotors, the aluminum rotor hat and aluminum caliper weigh substantially less than the cast iron original components.
Tires play a bigger role in your actual stopping distances, a stickier tire will allow more energy transformation (changing kinetic energy into heat energy at the friction point of tire meeting road), so if you ditch the all-seasons and strap on some performance tires, your braking distance will go down.
But in an enthusiast-driven car, braking distance is only one factor, and not the most important one. As above,
repeatability is important... this means that in performance driving, particularly like an organized HPDE, the margin with a BBK before brake fade or failure is much greater. Your brakes will be able to convert and dissipate more energy (again kinetic into heat) quickly and with more reserve capacity than the smaller OE components.
Not only that, but the durability aspect comes into play; the margin you have in terms of boiled brake fluid and cooked caliper seals is also much greater. Effectively, under the same use, a good BBK is under-stressed compared to the OE components.
This leads into your next excellent question about bias and clamping; you're discussing "brake torque" which is how much force the brake system applies to the axle. There is no need to increase brake torque whatsoever; with regular street tires, you can engage the ABS system already, which shows that the original brakes are already capable of generating more brake torque than the tires can handle.
More brake torque will not help at all!
So what that means in terms of a good BBK is that the same brake torque is applied (if just a "front only" kit), or that all four wheels are generating the appropriate torque to maintain good bias. The benefit you're getting from the BBK is in it's increased component size, which is the fundamental strength of better heat management.
How does this compare to basic improvements you can do with the original components?
No matter what you do to an OE-size rotor, you're not increasing it's heat capacity... and you really should avoid cross-drilled rotors (that's an entirely different discussion, but despite marketing hype, cross-drilling will actually decrease your braking system's effectiveness and they do not aid cooling - it's a "race look" component that some think looks cool, and that's about it). The various methods of slotting are a good idea and help in terms of surface water evacuation (as when driving in rain) and freshening the pad face, but that's about it. Anything else in terms of plating is simply cosmetic.
Brake pads, however, are an area of great improvement. A good ceramic "enthusiast" pad like the Hawk Performance Ceramic or Akebono ProAct Ceramic will give better initial bite (how the brakes respond to pedal pressure) and will also have a higher maximum heat range. This is not to say they are pads you should use at a track - track use always means use track pads, there is no such thing as a good "dual purpose" street and track pad. Avoid the advertised "dustless" pads as these are commonly known to have a "wooden" pedal feel and decreased rotor life. It's also important that you use the same (or very similar) pads front and rear because different pad materials have different coefficient of friction ratings, which can substantially change the brake bias. If you know what you're doing, "pad tuning" is a useful tool for adjusting brake bias (most useful for track/race cars), read more about that- [
CLICK HERE ]
One thing you're certainly right about... BBKs do look cool! In addition to the benefits listed above, the "look cool" factor is certainly an acceptable reason to get a BBK. After all, it's your car, and making it look cool is certainly your privilege!