A decoupling multivariable controller (DMVC) is generally considered more general than a multiloop controller (MLC). This is because a DMVC can eliminate the interactions in an MIMO process and result in better performance. Nevertheless, MLC may perform better than the DMVC while dealing with disturbance rejection. If the control objective is aimed at disturbance rejection, selection between these two types of controllers for better control is thus necessary. In this article, a method to assess the. performances of these two types of controllers for a given process is proposed. Given an MIMO transfer-function model, the achievable performance is derived; indices for assessing these two systems are proposed. By making use of these indices, a proper type of system (DMVC or MLC) can be selected in the precedence of designing the controller.