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Steering response will be improved with toe-out.
Straight line stability will be improved with toe-in.

Sometimes toe-in or toe-out is used for another effect; Tire-temperature.
For racing-tires it's very important to reach a certain temperature in order to deliver maximum performance/gripp.
If the tires stay too cool than toe can be used for the "scrubbing" efect,
The scrubbing also has another positive effect; It will scrub the tires clean providing extra gripp for braking and cornering.

Street cars often are set up with toe-in; For good straight-line stability cornering is sacrefied.
Race cars are often set up with toe-out; Straight-line stability is sacrisfied for good cornering.

If the suspension is independent; Toe-in or -out can also be applied to the rear-wheels. The effect on the rear-wheels is generaly the same as on the front.