Emerging Non Volatile Memories (NVMs) are considered as potential candidates for replacing SRAM in future processor architectures. They offer higher density and near-zero leakage power, which is particularly interesting to reduce the overall system energy consumption. Nevertheless, NVMs can suffer from higher access costs in latency and dynamic energy consumption. Existing literature covers a large panel of techniques to mitigate these issues. However, design space explorations on NVMs are rarely discussed. In this paper, we present a comprehensive design exploration phase based on the NVSim tool to identify relevant NVM technology configuration. Selected designs are evaluated at Last-Level Cache (LLC) of multicore architectures by using a fast tracebased simulation. Energy-Delay-Product (EDP) is often used as a prime metric to evaluate NVMs integration. This papers discusses the usage of the EDP by adopting two perspectives of analysis : i) LLC only and ii) entire memory hierarchy. We show that the former, widespread in the literature, could lead to biased conclusions regarding of the impact of the NVM. It is therefore advisable to use a global perspective to accurately assess changes on the memory hierarchy.