. When braking on dry or wet roads your stopping distance will be about the same as with conventional brakes.
You should allow for a longer stopping distance with ABS than for conventional brakes when driving on gravel, slush, and snow. This is because the rotating tire will stay on top of this low traction road surface covering, and effectively "float" on this boundary layer.
A non ABS braked vehicle can lock its tires and create a snow plow effect in front of the tires which helps slow the vehicle. These locked tires can often find more traction below this boundary layer.
Snow under pressure sticks to ice better than frozen rubber does. You want the tire to stop rotating so it can build up a 1/2 layer of snow.