This is what I can read from other US forums.

HPA gives you only the lower portion and the outer rim is not machined like the VWR subframe mount. The VWR mount gives you twice the mount (top & bottom) and with the rim being machined it's a perfect fit. So both design and materials.

Quote Originally Posted by Domz View Post
interesting... it is the design or materials used in the VWR that make it better?