My F50 setup was definetly much better than standard, although I was running standard rears that had not been touched since I bought it, and upon removing them, the rotors and pads were quite worn. So I guess with new rotors on the rear with decent pads, new rotors on the front and maybe a seal kit through the F50 calipers the setup might have been just as good as the Alcon kit I have now, but the availabilty of the Brembo F50 rotors and the money to freshen up the rear gave me the incentive to bite the bullet and get the Alcon kit..
I did not measure the braking performance by distance or lap times, but it felt much stronger under brakes, I guess new rotors/calipers/pads and great balance does that. I cannot compare lap times due to the fact my car has undergone more mods since the new Alcon kit went on the car, aswell as myself improving driver ability..