To achieve the specified geometry for an extruded profile together with a minimal degree of internal stresses, flow balancing of the die is required. To fulfil this requisite, a set of operating conditions/polymer rheological properties are assumed during the design step, which are particularly relevant in the definition of the extrusion die flow channel. However, fluctuations of the operating conditions and/or slight variations of the polymer rheological properties are expected to occur during long-term productions. The effect of these factors on the performance of an extrusion die will depend, among other factors, on its flow distribution sensitivity. In this work, four extrusion dies optimised (balanced) using different design strategies are evaluated in terms of their absolute quality (when used in the optimal conditions) and in terms of their stability to the operating factors considered. For this purpose, a computational code, based on the finite-volume method, is used to perform the required non-isothermal three-dimensional numerical simulations of the flow under conditions defined by a statistic Taguchi analysis.