Impact of the inclusion of higher order modes in the waveform model employed to evaluate the Ω_GW spectrum. On the left: 95% confidence on the spectrum including the uncertainty on the PLPP mass model and the local merger rate, assuming a fixed MD redshift evolution. On the right: percent difference %ΔΩ_GW(f) between Ω_GW spectra calculated using the same event samples, shown as dashed and dotted curves on the left panel.