Since Shaun's answer accurately addresses the main question, I am going to address this in a slightly non-technical, business-strategy way that does not deal directly with SEO rankings.

As a business, the blog is really to get people to learn about you, your e-commerce store, and your products. I'd suggest that you consider a self-hosting account on Medium so that you get the best of both worlds - your blog becomes more discoverable due to Medium's extensive network and you still have a custom domain name (blog.domain.com). This may or may not fit in into SEO wisdom, but works very well from a business perspective. I'm not sure how your affiliate marketing attribution is done, but I don't imagine that will be impacted whether you use Medium, Wordpress, or a simple HTML page to power your blog.

I've seen more and more companies move away from running after rankings through technical SEO manipulation. As long as your content is relevant to the audience coming to your website and they spend more and more time on your website, your ranking will continue to improve. Any short-term "hack" you make to improve rankings outside of content will be short-lived. So do you what you'd do normally to get more business for your business.

Great question! Content marketing (the use of content to attract a targeted audience) is a powerful and effective tactic for successful ecommerce. And blogging is one of the most effective methods within that tactic.

As you are aware, the more detailed and targeted your blog content, the more likely you are to rank higher in the search engines for your chosen topic or product. The higher you rank, the more human traffic will come to your site.

All that said, there is little to no difference between maintaining your blog content on a sub-domain versus a sub-directory.

EXAMPLE:
- subdomain.yourdomain.com, OR
- yourdomain.com/subdirectory

The key is to host your blog on your domain and not elsewhere:

EXAMPLE:
- yourblog.blogspot.com

In the above example, the content is hosted at Blogspot, giving them the search engine "credit". It is always best to host your optimized content on your domain.

For some entrepreneurs, the technical considerations of setting up their own blog may be too daunting to attempt (that is why sites like Blogspot and Wordpress.org do so well, they make it very easy for folks to get their blog up and running quickly, with very little technical know-how). The drawback is the search engines are not sending traffic to your site, but instead to a third-party.

There is a lot of value in having a domain with quality, original content. If you want to have traffic going to your ecommerce site, I highly recommend you blog on that same domain. Keep in mind, your blog content should be interesting to the audience you are hoping to attract.

All the best,
-Shaun

A lot of value in having a domain with quality and original content. If you are wanting to have traffic going to your ecommerce site I would highly recommend you blog on that same domain. but keep in mind that your blog content should be interesting to the audience you are hoping to attract.