Generally speaking, it goes as the following...
- Positive rear can help with acceleration and handling, and can also help with the overall stability of the vehicle.
- Negative rear can help with the steering angle (i.e. powersliding/drifting) and can also offset oversteer to some degree.
- Positive front can help with straight-line stability (not to be substituted for caster). There is the possibility the vehicle may become twitchy under braking and turning into a corner.
- Negative front can help with steering response and handling, but just as the positive adjustment there's the possibility of the vehicle becoming unstable or just not handling as well as it did prior to the adjustment(s).
And of course using excessive values can increase tire wear, diminish tire grip and you'll likely have to nurse the vehicle too much for it to be drivable. Hopefully, I didn't misunderstand the question.