Using virtual models of a real environment to improve performance and design effective and efficient user interfaces has always been a matter of choice to provide control of complex environments. The concept of Dual Reality has gone one step further in synchronizing a real environment with its virtualization. So far, little is known about the design of effective Dual Reality interfaces. With this paper we want to shed light on this topic by comparing the strategies, performance and efficiency in a real, virtualized and a DR setting given a complex task. We propose a cost and efficiency measure for complex tasks, and have conducted an experiment based on a complex shelf planning task. Our results show that for certain tasks interacting with the virtual world yields better results, whereas the best effectivity can be observed in a Dual Reality setup. We discuss these results and present design guidelines for future Dual Reality interfaces.