Subfolders and Subdomains have their own pros and cons if viewed from business viewpoint. However, these day’s website owners more interested in focusing their efforts on SEO.
Which one to choose Subfolder or Sub Domain for my blog promotion?
If you are thinking of launching a new blog, then using a sub-folder will bring better rankings on search engines.
Search engines will try to equally distribute ranking power among other pages on the blog including home page. If your blog is popular and generates good quality backlinks, then your main domain will also benefit from the activities on your blog.
I prefer a subfolder for blogs(http://www.abc.org/blog/) because the link juice which is sent to that blog is going to be naturally distributed to that main domain, and other subfolders under the domain.
Futhermore, the logo, home page and other links back to the subfolder. If you set this up with a subdomain, by default, the links in the forum/blog itself will all point back to the subdomain. So, with a subfolder, both the inbound and internal linking structure favor the entire site.
When should I use Subdomain?
Subdomain can turn out as a powerful technique to host a blog or a different sub-site with a completely different business theme.
If your main site is about gaming, then you can create a Subdomain for educational purposes.
With a subdomain, as i already mentioned Google treats an an separate entity, which is good for owning the results and one’s reputation management. However, Google and other engines will generally not list more than two of these subdomains in the search results, unless those subdomains can prove to Google that they are independent and relevant entities.
SEO Definition for Subdomain – Subdomain is treated as a separate website, which is “Technically connected” with the main site (Google considers technical connection). However, you cannot pass link juice from Subdomain towards main site or vice versa. If you intend to do so, then you have to interlink your Subdomain with your main website.
SEO Definition for Subfolder – Subfolder can be used as a Subdomain catering to different related topics. Subfolder is very much “SEO connected” to the main site and any activity (good or bad) on the subfolder can have positive or negative impact on your main site’s SEO rankings. If you are pasting duplicate content on your subfolders, then it will lower the search engine rankings of the main site. Therefore you need to be careful while using subfolders for different sections.