In this paper, a comparison is made between two models used in the determination of procedure described in a previous work. The second one (calibration methodology), valid for power law fluids, characterizes the rheological properties of suspensions by flow curves which present the dependence of the shear stress on shear rate. Tests of statistical significance do not allow us to distinguish between them. Since the mathematical complexity of the calibration methodology is lower than that of the improved numerical method, it is concluded that the former is preferred to the latter in the determination of rheological parameters of power law suspensions.