Long-span bridges are sensitive to wind-induced forces. In this paper, we evaluate the influence of the assumptions in the semi-analytical aerodynamic models on the dynamic response of a bridge deck using comparison metrics. These metrics are constructed in such way to evaluate the differences in the signal properties of the time-dependent response. The signal properties include the time-varying frequency and magnitude content, phase and stationarity. The behavior of the metrics is first studied on illustrative examples. Finally, the metrics are used to quantify the discrepancies in the response of a streamlined deck, obtained by utilizing a numerical and two semi-analytical models. The results of the study provide deeper insight into bridge aerodynamics.