The difference in weight transfer should be negligible considering the same overall grip and the fact that stock brakes are powerful enough to lock up the tires already. Most street cars are set up with excessive front bias as a car is more stable under braking this way and therefore safer for the average public. Most cars will brake faster overall by adding slightly more bias to the rear than comes factory. This is the only way most brake kits are going to improve stopping distance given that OE brakes are usually strong enough to lock up street tires as it is. The only benefit to larger brakes is that they are less prone to being overheated and losing braking power as a result. Most of these cobbled together kits feel better due to less pedal effort for a given amount of deceleration but I would be willing to bet most of them have longer one stop stopping distances than a good working stock setup.
