Sample properties. Left: redshift-mass distribution of the clusters used in this paper. The SZE-selected clusters comprise a subset of 44 systems from the Planck Early SZ sample (Planck Collaboration VIII 2011) at z < 0.5 and a further 49 clusters at z > 0.5. REXCESS (Böhringer et al. 2007) is an X-ray-selected sample of 31 objects at z < 0.25. Right: stacked histogram of the mass distribution. The REXCESS sample has a lower median mass than the SZE-selected samples.