[Arran]

I don't think that there is inherently anything wrong with either a lacquer, or a shellac finish, depending on the grade of the lacquer or the shellac and how it is applied. My grandfather was a furniture finisher, he took an apprenticeship and the method he learned was French polishing, with shellac, which involved applying the shellac step by step, by hand, with a pad or tampon. I can quite assure you that if you use the French polishing method of applying shellac the shellac does penetrate the wood, the main disadvantage is that it is slow, but it really brings up the grain, is easily repaired, and it has a sort of sheen that's hard to match.
  I would not use polyurethane on any piece of furniture unless it was intended to be kept outdoors, in spite of popular misconceptions it is not an eternal finish, as it ages it tends to turn a sort of disgusting green colour, and ultraviolet will ruin it just like any other finish. It also takes forever to cure, weeks if not up to a month or more, and if you mess it up the only way to get it off is with paint and varnish remover verses acetone or alcohol for lacquer and shellac, no thanks!
Regards
Arran