You want to expose your website to as many people as possible. Google is the king of search. Everyone is using it. The more Google exposes your website from the search results, the more traffic you will get. So, make it easy for Google to index your website. Submit your sitemap to Google. What Google accepts as a sitemap can be found at https://support.google.com/webmasters/answer/183668?hl=en
Google does accept RSS as sitemap. Luckily, by default, Drupal comes with a default rss.xml, e.g. http://openwritings.net/rss.xml. So, I submit it through the Google Webmaster Tool.
There multiple modules for sitemap but for I'm happy with the RSS. I don't want to clutter my website with gazillion of modules.