Hi Richard,
Having the link positioned in the upper navigation will help ensure that the search engines view that link as important. Just as importantly, it helps consumers know that the link and information in the blog is important.
Placing links in the footer only remove them from visibility considerably, and search engines can detect link placement on the page, placing less weight or value on that link.
Also, if you are building high quality content in your blog to engage consumers then having that link in an appropriate area increases the potential of your audience finding that content, engaging with it, and supporting what you.
Good luck in business!