It doesn't matter like it used to.. or in a traditional SEO sense like you may be thinking. The most important thing now for SEO is to make sure that your blog is being promoted well and that it's an active part of your social media promotions along with your website.

That being said, if it's on topic then I would put it in a directory. This will increase the overall authority of your domain as long as you actively link from your blog posts to relevant pages throughout your website on a consistent basis.