In all-wheel drive, the car's computer sends more power to the tires that are receiving more traction, while in four-wheel drive, the power is split evenly between the tires. Four-wheel drive vehicles perform better when there is some give in the terrain underneath the tires, snow or mud, for example.
When turning a vehicle, the two wheels on an axle need to spin at slightly different speeds due to the different turning radius, something that is not a feature of 4WD vehicles. This can cause the wheels to lock up on ground that the tires grip well, such as pavement. Because of this, 4WD handles better on mud, snow, dirt, and gravel than in urban areas. The loose terrain allows the wheels to slip a little, preventing the wheels from locking up. On an AWD car, the on-board computer controls how much power any wheel has at any given time, making it a better choice for everyday driving in the city.