For the search engines, .xml. For your users, .html (and only if you want to help them navigate your large site).
Use sitemap.xml to crawl your WebPages better. I have no sitemaps in my blog site. But Google crawls and index new postings within a few hours. Anyway, so far I know, sitemap is useful.
Very interesting topic I think XML sitemap is good to crawl your site better in search engines. If your site navigation is good then it is not necessary to use sitemap but sitemap is a additional tool for serach engines.
Google Webmaster tools makes it easy to submit sitemaps. They may not be "necessary" but I'd recommend them because they are typically used for both indexing and for navigation. Hope that helps
.XML sitemaps are meant for crawlers and spiders while html sitemap is meant for visitors. Visitors have a primary choice to browse site by navigating thro links and can have html sitemap as secondary choice. So, from SEO perspective, XML Sitemaps are must. HTML sitemaps are also good, but mostly for visitors, It doesnt fulfill the purpose of XML Sitemap for bots and crawlers.... goodluck..
if you using the sitemap for the search engines i recomment .xml if it's for users maybe .html is better but since most of the time we use the sitemap for the SE ... i guess xml wins big time
both html and xml are good, but I think that xml is more practical, cuase most of the search engines will accept that better than html. Anyway, you can create both sitemaps with Sitemap Writer Pro.
.XML is best beside you can used gnzip sitemap too that compress your original sitemap. HTML is for GUI where people can easily navigate your website. Through .xml it never possible.
Both sitemap our very important and gives advantage to our website, XML sitemap helps to crawl our website through robots and html sitemap user to search our website very easily.
Both the site maps are useful in its own way. xml site map is useful for search engine's and html for user's.Its easy to understand.
i think all site maps are good as xml sitemap is google freindly, .txt is yahoo freindly and .html is msn, bing freindly.
XML Sitemap is usually called as spiders sitemap, it is meant for spiders to crawl.It make spiders to crawl the pages.Whereas HTML Sitemap is meant for Human, it helps a visitor to reach every page of website thus it is for users who use for easy navigation from one page to another page easily..