How different are the Liège and Hamburg atlases of the solar spectrum?

Context. The high-fidelity solar spectral atlas prepared by Delbouille et al. (Liège atlas, 1973) and the atlas by Neckel (Hamburg atlas, 1999, Sol. Phys., 184, 421) are widely recognised as the most important collection of reference spectra of the Sun at disc centre in the visible wavelength range. The two datasets serve as fundamental resources for many researchers, in particular for chemical abundance analyses. But despite their similar published specifications (spectral resolution and noise level), the shapes of the spectral lines in the two atlases differ significantly and systematically.