Nikon 400mm f5.6 ED AiS or 300mm f4 AF-ED (non AFS) + 1.4x Kenko Pro 300 DG

Which one would deliver better Image Quality (IQ) ?

AF and Manual Focus is not the deciding criteria.

Will the 400mm f5.6 give inferior IQ owing to its old technology ? Or will the 300mm and TC combo give inferior IQ because of adding the TC ?

M.