Driver interview while driving an All-Wheel Drive 2010 SRX  helps explain in lay-person’s terms why an All-wheel drive vehicle is superior as an all-weather vehicle:

For 2010 we have an all new, All wheel drive system.  The new feature is an electronic limited slip differential that is able to deliver torque across the rear axle of the vehicle to put power to the tire that has traction available to it.   This is really helpful in terms of your safety and security, making the car go where you want it to, getting started in tough conditions on hills and so on.  Just a great feature, and makes the car really enjoyable to drive when the going gets tough like this.

One of the great things about our Cadillac systems is the refinement that we offer, the smoothness of application and the sense of security that  the systems will give to you as you drive under tough conditions.  The vehicle  feels very sure footed, and makes you confident that you are going to get where you want to go, and get there safely.

This animation shows the system with shift in torque front to back or left to right:

You can read more about the AWD Haldex System here.  The new Cadillac XTS Platinum Concept car uses a similar AWD system as standard equipment.

To date all-wheel drive systems do not give advantages in terms of absolute cornering on a dry surface.  They can be an advantage in acceleration on a slick or dry surface, but because traditional AWD systems also brought a significant weight penalty the net advantage of the additional traction is more than offset by the added weight and thus reduced acceleration.  The new system is somwhat lighter, but also responds more quickly than traditional systems.