Well lad, it depends hardcore!! Like with all the parts where u can change something u'd have to try out which works best. As i am not an native englishman and do not speak and write perfect, i try to give u some hints and tips on this one:
First of all: Is the car FF, FH or MH? The brake balance is here to optimize the stability of the car during the braking, also the amount of power that is used to make them stop the car brutally.
As an FF car is already quite stabile overall (it pulls the car, makes everything very stabile) you can put more force on the frontbrake, usually i set them 6 front and 5 back for a start with all cars to try it out. As long as the car remains stabile during the brake process u can put it higher and higher, but u have to avoid bumping (happens when u got a suspension which is too hard, set the suspension very hard and try to set the brakes on 10 and look what happens when u brake hard)
An FR has the tendency to oversteer already while braking. In the most FR cars u can use the same settings as above, but if u harden the suspension too much the car starts bouncing, meaning u lose control. Which is more likeable with FR cars. Then u set the balance to F5 R6 to start off.
MH cars got very good balance overall (Elise f.e.) and they react very fast in corners (they mostly are very light), set the balance to F4 and R7, this is what i do for a start.
Overall u could say: if the brakes are set harder to the front, the car brakes much faster, but it is also gettin instabile while braking. If the brakes are set to the rear end, u lose worthfull meters while braking, but u will be very stabile while braking.
Racecars often cannot be set too hard because the suspension ist mostly very hard and the cars light.
There are lots more things to look out for, but since u seem to "start" trying out i guess these are some helpful tips.
Cheers mate