In this study, a new system assessment metric is proposed to evaluate the robustness of system architectures to different stakeholder perspectives and decomposition preferences. Typically, the decomposition of a system architecture into a modular configuration is based on the function-based perspective of the design teams, which can be different from the perspectives of other stakeholders such as the manufacturing teams and field service organization. In this paper, a system architecture is decomposed into different modular configurations on the basis of the preferred perspectives of various stakeholders. The generated configurations are then compared to function-based modular configurations in terms of the diffusion of the original function-based module components into modules generated from different perspectives. The degree of diffusion is measured using a newly proposed entropy based metric referred to as the module diffusion index. The proposed metric provides stakeholders with a quantifiable measure of the robustness of a particular system architecture with respect to the preferred decomposition strategy of different stakeholders. The proposed metric can be used to assess different system architectures in terms of their robustness to perspective-based decompositions. A case study is conducted wherein different mechanical clock architectures are assessed in terms of the robustness to different perspective-based decompositions to demonstrate the effectiveness of the proposed metric.