I haven't done any traditional gravure, but I'll say that I've seen lots of poly-gravure prints and they have never come to the level of perfection evident in the copper-plate gravure prints tipped into wonderfully expensive old hard-bound books. It may be possible, but I'll have to have it proved to me. I've never seen a poly-gravure print done by someone who has also mastered copper-plate gravure, of course. The craftsmanship is certainly a factor; it may even be the deciding factor, but I think not. The plate and the process do make a difference.
Has anyone compared the quality of the polymer photogravure to the copper photogravure process?