If you try to rank your category pages and want to make them less "thin-affiliate" it would help to add some unique content (like these category descriptions) on these pages.
Imo using 300-word category descriptions as separate stand-alone blog posts will not make much sense for a visitor.
What useful information would get a visitor out of such a blog post? I would rather use blog posts for adding latest news, reviews, comparisons, how-to information,...
Imo you should not think "in SEO terms". Ask yourself what makes sense for the visitor.
If linking from one category description to another related category or another page on your site will help a visitor's browsing experience feel free to link.