How does PageRank pass through a backlink on a subdomain vs. subdirectory?

[mcelano_compassknowledge.com]

Scenario 1: I earn a link on exampleblog.root.com/example-page/. The DA is 90, but it's a brand new page so PA is 0. Subdomain is also new, zero backlinks.

Scenario 2: I earn a link on root.com/example-page/. The DA is 90, PA is still new so 0 for now.

My assumption is that PR will flow from the homepage through the subdirectory then ultimately to my domain. If the subdomain doesn't inherit any of the root-level metrics, then should I even be worried about the DA in scenario 1? What are the seo implications between the 2 scenarios?

[CleverPhD]

Subdomains are considered separate sites and so normally you would consider all the link metrics separate.  That is why the most common advice is to use subdirectories for content sections vs subdomains.  That way any link equity/page rank you acquire for links into the subdirectory flow up to the main domain.

You also need to be careful not to run into duplicate issues with a www vs non www versions of your site as those two subdomains are seen as separate entities by google.

If you want to consolidate link equity, 301 redirect all the pages in the blog subdomain (i.e. blog.root.com) to the equivalent subdirectory (root.com/blog) then you can have a unified single set of pages/URLs to focus on.