I am one of those strange guys that actually PREFER Quanjude more than the others. I am Chinese, speak the language, and very familiar with Beijing and have eaten at all the major known and unknown duck joints.

If asked why I prefer Quanjude is because of the roasting of the skin. All the ducks have a crisp outer skin, but at Quanjude it seems to me that the underside fat on the duck skin is much more "vaporized" and I feel less like I am eating chewy duck fat.

Anyways my two cents..

P.S. My own opinion only applies to the main branch Quanjude at Qianmen facing Tiananmen.