Ratio between the rest-frame peak energy from synchrotron model fits, $E_{p,z}^{\mathrm{Sync}}$, and Band model fits, $E_{p,z}^{\mathrm{Band}}$, as a function of $E_{p,z}^{\mathrm{Band}}$ (left-hand panel) and low-energy break, α, histograms (right-hand panel), both relative to GRBs in the synchrotron single-bin sample. Parameters from GRBs associated with fast-cooling spectra (ν_m/ν_c >  3) are shown in red, while the ones associated with intermediate-cooling spectra (1< ν_m/ν_c <  3) are shown in blue.