Ratio of XMM-Newton and Chandra gas density profiles published by Vikhlinin et al. (2006, 2009a) and Planck Collaboration XI (2011; PXI), obtained using independent analysis techniques. The XMM-Newton and the Chandra profiles are derived from deprojection and parametric model fitting, respectively. The vignetting correction method is different (see text). The point source and substructure masking and centre choices are also independent. The black solid (dashed) line represents the median (weighed mean) and the grey shaded area its 1σ confidence level. The dotted horizontal lines represent the ± 5% levels. At large scale the profiles show good agreement in the shape, with an average offset of ~2%. In the inner regions differences are dominated by the choice of the centre. The difference between the centres ranges from 1 to ~14 arcsec (<0.02 R₅₀₀ in all cases).