How valuable and/or effective for search engine rankings are links from your sub-pages compared to links from totally different websites of a similar theme? The purpose of this question is to prove to someone else what the difference in effectiveness sub-page links have compared to links from other sites.
Links from subpages distributes the PR on your site, links from external sites increases the PR on the site.
Could you say, links from subpages distribute PR on your site, but don't increase SE ranking with any significance and links from external sites increase your PR and your rankings?
Yes partly. The internal navigation also influences the SERPs. For example lets say you have a site with 250 webpages. One of those pages are important but kept deep in the navigation tree. So you make a link on all of the web pages to easily reach that page, a lot of PR gets distributed to it and that particular page ranks better then let's say the other 200 web pages that are on the same level of the navigation tree. You get my point?
Yes I do, so links from subpages do help SE rankings, but you should really link them sitewide to notice any real increase in rankings?
Depends fully on your navigation structure. I only did an example. If your web sites are of similar importance I would make each web page reached within 2 clicks, if not possible with a navigation bar then use a sitemap and a sitewide link to it. Usually the index page is also of more importance so I would have a sitewide link to that one as well, both for SEs and for visitors. Also think about the visitors.
OK, I have a 350-400 page site and I want to optimize (get higher rankings for) some pages more than others. For those pages I wanted to optimize the most, would creating links on all or most of the 350-400 pages that are directed to the pages I want to optimize the most be specifically beneficial for those pages I want to optimize?