I think html sitemap is always useful to have a way to reach deep pages with few links. The deeper google crawls the lesser pages it crawls. I think the best option is to have all your pages at a distance of 3(at least 4) links from your homepage. This may be difficult for the site structure (imagine a blog with plenty of articles, there are some old hide ones) but with an html sitemap i tmay be easy to achieve.
@aristotle: it seems quite the same thing to me. Why not noindex them so Google won't send traffic to them, maybe is better show your homepage for that query. Noindex will prevent those page from showing but will maintain the crawling of its links.