Comparison of canonical thin-shell and thick-shell models (X = 0.6) for the PWN-SNR population. The black ellipses represent the region in the characteristic plane containing 98% of the expected Galactic PWN-SNR population. The points represent the models of Table 1: the red dot at the center is C0, yellow triangles represent models of the sequence S#, and magenta squares show those of L#. The upper panel represents the relative difference in the time at which reverberation begins $\mathrm{\Delta }{t}_{\text{beg,rev}}=t_{\text{beg,rev}}^{\text{thin}}-t_{\text{beg,rev}}^{\text{thick}}$. The lower panel represents the relative difference in the energy content of the PWN at the time at which reverberation begins $\mathrm{\Delta }{E}_{\mathrm{p}\mathrm{w}\mathrm{n}}=E_{\mathrm{p}\mathrm{w}\mathrm{n}}^{\text{thick}}-E_{\mathrm{p}\mathrm{w}\mathrm{n}}^{\text{thin}}$. The green line separates systems with a positive difference from systems with a negative difference.