Sitemaps have always been a part of best Web design practices. But, since the time when search engines first adopted sitemaps, they have become even more important. A sitemap, along with offering easy navigation and better search engine visibility benefits, informs the crawlers immediately about any change on your website so that the page is indexed faster. From an SEO point of view, we suggest you to do away with a conventional sitemap and create an XML sitemap.
Read this Google Webmaster Help article on how to manage your sitemap.