Patents add the fuel of interest to the fire of genius.
A registered design aims to protect the external aspect of an object, and is not related to the functionality of the object. For example, a new design for a chair, cup etc can be protected by a registered design. It is much easier and faster to obtain a registered design compared to obtaining a patent. Although a design offers less protection than a patent it can be a good complement to a patent application if you wish to protect both the functionality and the design of an object.