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

I am considering buying an Audi car and I noticed that some models come with Quattro while others come with Quattro with Ultra. Can you explain the difference between the two and which one should I choose?

Quattro is Audi's all-wheel drive system that uses a mechanical center differential to distribute torque between the front and rear axles. Quattro with Ultra, on the other hand, is a more advanced version of Quattro that uses an electronic multi-plate clutch to selectively engage the rear axle when needed for better fuel efficiency. If you live in an area with mild weather, Quattro with Ultra might be a good choice. But if you often drive in harsh weather conditions, I would recommend going for the traditional Quattro for better traction and stability.