Brake help is like a very simple kind of ABS. All it does is to reduce the amount of how much your brake pedal is depressed, as soon as a wheel is about to lock up. This means it always affects all wheels, and can considerably lengthen the brake distance in certain situations.
Personally, I have everything besides auto-clutch turned off, and as soon as I get my G25 that will be off too. But it's entirely up to the driver what he wants to have turned on/off. The more options are on, the "easier" the driving is, but the less control and immersion you get.