What is the difference between Quattro and Quattro with Ultra in the Audi A6?

I have been researching the Audi A6 and have noticed two different versions of Quattro - the regular Quattro and Quattro with Ultra. Can someone explain the difference between these two options and which one is better?

Quattro is Audi's all-wheel drive system that continuously distributes torque between the front and rear axles for optimal traction and handling. Quattro with Ultra is a newer version that can disconnect the rear axle when not needed, resulting in better fuel efficiency. Both systems are capable and reliable, but if you prioritize fuel efficiency, Quattro with Ultra is the way to go.

The difference between Quattro and Quattro with Ultra is mainly in the technology used. Quattro utilizes a traditional mechanical center differential for power distribution, while Quattro with Ultra uses an electronically controlled multi-plate clutch. In terms of performance, there is little difference between the two, but Quattro with Ultra may have a slight edge in fuel efficiency due to its ability to disconnect the rear axle.

As an Audi mechanic, I have worked with both Quattro and Quattro with Ultra, and they are both solid options for all-wheel drive. Quattro with Ultra is more advanced and can save on fuel, but it requires more maintenance compared to the regular Quattro. In my opinion, if you don't mind a little extra maintenance, go for Quattro with Ultra for its added efficiency.