Domains don’t have PR. PR is not assigned to websites, it is assigned to individual pages.
When you create a new page, whether, on a brand new website or a high PR domain, they are both treated the same by search engines. What makes a difference is the inbound links to those pages. Many sites like Ezine and Hubpages have a community and they provide internal link structures that will pass link juice to the new pages that you create within their community. That is where the extra value comes from.
You can pass that same community like benefit onto a new blog page if you get inbound links of similar value pointing to the new pages you create. The obvious advantage of creating content in a community like HubPages is the built-in links and traffic from within the community.