What is the difference between Audi's Quattro system and Quattro Ultra system?

I would like to know the specific differences between Audi's famous Quattro system and their newer Quattro Ultra system.

Audi's Quattro system is a permanent all-wheel drive system that utilizes a center differential to send power to the front and rear axles as needed. Meanwhile, the Quattro Ultra system is a more modern, on-demand system that uses a series of sensors and electronically controlled clutches to continuously monitor and adjust power distribution.

One major difference between the Quattro and Quattro Ultra systems is their weight. The Quattro system tends to add more weight to the vehicle due to its mechanical components, while the Quattro Ultra system is lighter and more fuel efficient.

The Quattro Ultra system is generally considered an upgraded version of the Quattro system, offering improved performance and efficiency. However, some drivers still prefer the traditional Quattro system for its reliability and familiar feel.