When Magento generated my sitemap.xml, the total amount of links are much fewer than the URL Rewrite links. Of course I understand that in URL Rewrite Management page, many of the links are redundant.
That's why I truncated the core_url_rewrite first then run the reindex. So now all the links are System generated links, not Custom links. But still the total amount of links in URL Rewrite Management is much more than the sitemap.xml.
I've enabled Product, Category and CMS Pages in System-Configuration-Google Sitemap. But still the total amount of links in sitemap.xml is much fewer. I would expect the same or not too many different.
Any reason why?
Use Categories Path for Product URLs
in System->Config->Catalog. If you have many nested categories, then there are many different paths to the same product - maybe those paths are not included in the generated XML sitemap.