Hi Paul,
thank you for directing me to FastStone Viewer, which to my surprise even started in German without me choosing a language.
I knew it was ‘there’, but never tried it, as – apart from Windows … (sRGB colour space only; same as IE) – I have been using XnView (quite shortly), IrfanView (at work), FastPictureViewer (for culling) and ‘due to this forum’ now FastRawViewer. Otherwise, I have been organizing all my stuff with TotalCommander, which I prefer a lot to Windows’ own explorer.
Well, there are a tons of options in FSV, I have to see about and might report some time – but still like to have that compare option in PL. 
thank you again, Wolfgang