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If all other things are equal AND you all have some crawlability issues, yes it could be a major factor. For example, if you have deep pages that are not indexed well then linking to them outside of the sitemap could help. Just because a page is in the sitemap doesn't mean Google wants to index it. If it has zero other links (either internally or externally) and the content is a little "thin" they may choose not to include it. Adding a decent internal link could make the difference there. If all other things are equal AND those pages are indexed and linked to from your crawlable navigation, yes it could be a moderate factor if your competitors are interlinking from body copy and the only place you link from is the navigation - as these types of links are not treated exactly the same. That's the short answer. The long answer is - it's complicated. Feel free to stop reading here if you really don't care about possible complications. Some sites go too far on their interlinking strategy and end up with a penalty. I've seen this happen on a few Wordpress sites that use a plugin to automatically link every single instance of a phrase to a specific landing page. That just doesn't look natural, and you could end up getting filtered or penalized at the level of the page or, more likely, for that specific anchor text. Another thing to look out for is future scaleability. For example, I don't often like to hard code links to specific products within the body copy of an eCommerce site because products tend to come and go. What you'd end up with a few years later is an avalanche of 404 errors that you'll have to manually go in and fix. I tend to leave product interlinking automated (e.g. Related products widget) and save the hard-coded links for linking to category pages, which tend to stick around longer.