If you are thinking which one of these XML sitemap Or RSS/Atom Feeds is best for optimal crawling then Google says use both. In the recent post, by Google Webmaster Central Blog, it says that it’s not an either/or question. The answer is to use both. It also talks about some other best practices such as including URLs, how often the XML sitemaps should be updated, last modification time. If you are one of the webmaster or SEO experts, we will recommend you to read the Best practices for XML sitemaps & RSS/Atom feeds.
As per Google:
For optimal crawling, we recommend using both XML sitemaps and RSS/Atom feeds. XML sitemaps will give Google information about all of the pages on your site. RSS/Atom feeds will provide all updates on your site, helping Google to keep your content fresher in its index. Note that submitting sitemaps or feeds does not guarantee the indexing of those URLs.
