Ratios between the integrated gas masses within R₂₅₀₀ and R₅₀₀ obtained from the XMM-Newton and the Chandra data. For all panels: the solid line represents the identity relation. Left panel: XMM-Newton gas masses obtained by Planck Collaboration XI (2011; PXI) vs. Chandra gas masses from Vikhlinin et al. (2006, 2009a). Central panel: Chandra gas masses derived from the pre-correction (photon weighting) method compared to those published in V06/V09. Right panel: XMM-Newton and Chandra gas masses obtained using the same analysis method (photon weighting method and non-parametric deprojection of the surface brightness profiles.