In this paper, we propose a novel method for selecting the transmission configuration in Spatial Modulation (SM) based multiple-input–multiple-output (MIMO) systems that provides the desired relative contribution of Spectral Efficiency (SE) and Energy Efficiency (EE) in the overall performance. This is done on the basis of a function proposed here called Weighted Efficiency Function (WEF) which takes into account both SE and EE simultaneously in the optimization. Here, we have considered the generalized model of the SM (GSM) to construct a set of operating modes incorporating the different system parameters. The goal of this work is to select the most appropriate modulation scheme and number of RF chains that maximizes the WEF. This selection is bound by certain constraints on power consumption, data rate and Symbol Error Rate (SER). In the end, we use simulation results to evaluate the performance of the proposed methodology and compare it with the state of the art.