Maybe we can get some of the dudes that track cars to have their say? I'm merly stating from my own experience (on a bike more then car) that I prefer full control on the brakes, you shouldn't jam on the brakes so you lock them either way... the feel I got in the car was that (might been due to them boiling) it was hitting on and off when it really shouldn't... personal vote is OFF and if you lock your wheels you've misscalculated where you're braking SHOULD have started
Braking point, entry point, apex, exit... vroom vroom
Maybe MRLizard can point some input in here? Or someone else that has race track experience / training etc...