Unless you’re in the thick of the search marketing business instead of the fringes, it’s quite accurate to say that a lot of the practices are downright mythical. Search Engine Land wants to debunk 36 of those once and for all. Here’s #4:
Having an XML Sitemap will boost your Google rankings. I just heard this one from a fellow panelist in an SEO session at a conference I presented at within the last month (I won’t mention who, or which show.) This made me cringe, but I bit my lip rather than embarrass and contradict them in front of the audience. Should I have spoken up? Did I do the audience a disservice by leaving this myth unchallenged? I struggled with that. In any event, Google will use your sitemaps file for discovery and potentially as a canonicalization hint if you have duplicate content. It won’t give a URL any more “juice” just because you include it in your sitemaps.xml, even if you assign a high priority level to it.
Most of the items in the list apply to Google and may or may not work the same way for other search engines such as Yahoo. For example, meta tags do not carry weight for Google but for Yahoo, they do.