What is the difference between quattro and xDrive?

I am considering buying an Audi or a BMW but I am not sure about what the quattro and xDrive systems do and how they differ. Can anyone explain?

Quattro is Audi's all-wheel drive system while xDrive is BMW's. Both systems distribute power to all four wheels but quattro is more performance oriented while xDrive offers better traction in slippery conditions.

Quattro uses a planetary gear system to distribute power between the front and rear axles, while xDrive uses a multi-plate clutch. This results in different handling characteristics for the two systems.

Having owned both an Audi with quattro and a BMW with xDrive, I can confidently say that quattro is more fun to drive and offers better handling in corners. xDrive is better for everyday driving and bad weather conditions though.