I have been through a couple of different pads on track and posted my experience
here. I just wanted to remind everyone here that if you want better braking on street or track, all you really need is suitable pads and brake fluid. You don't actually need a BKK. Take it from someone running a BBK.
Want more bite on street? Get pads with higher friction. They will dust more and things will wear faster, but they feel great.
Want legal pads? Sorry they will have roughly the same friction coefficient as oem pads.
Want to be able to push lap after lap on track? Get full-on track pads. Not sport pads. Not track day pads. Full track pads. And don't run them on the street.
You can get a BBK for many good reasons. Looks. Weight. Adjusted brake bias. Larger pads and more even pad wear. Longer or shorter pedal travel. Lower chance of piston seals leaking due to overheating etc. But ultimately your stopping distance on the street is decided by the tires you run. Not the brakes.
The rest is just about feelings. And most of the brake feel will come from the pads and how well they are bedded to the rotors. As an example, I got slightly longer brake pedal travel with my bbk, because the pistons up front were a wee bit larger than OEM, but this was altogether compensated for by running higher friction pads that bite as soon as they hear the shadow of a rotor. On the other hand, you can run the best BBK, and pedal feel will still be terrible if you run terrible pads.