Is there a difference between text links that are generated by forum comments as opposed to blog and article links? It looks like google gives us more credit for comments on forums than for articles that we write and submit to good ranking article websites and press releases. These are all doFollow websites and none of them show up as primary links with google. Primary links to me are the ones that show up in google without putting a space in between your www and the rest of your url when checking for links.
It is hard to tell what Google thinks. I think articles get more relevence and they can be picked up by others giving you more links. It depends on how competitive keywords are, content surrounding your keywords and other factors.
I think it depends more on the PR, quality, relation to your content, and number of outbound links. As long as the link is Do-follow, google doesn't care what it's posted on.
Posting links on high PR sites that are related to your site are the best links you can have. Does not matter if they are on a forum, blog or article. Also, the less number of outbound links from the site you are linking from means more "linkjuice" will passed to your site.
how do you come to that conclusion? forum signature links are very poor quality links and will hardly help you in SERP ranking. a well written artcile submitted on good article directories will not only give you quality backlinks but will also send you traffic to your site
Completely wrong There is a google patent for ranking websites based on the freshness of the content around links, so if you are using forum comments or signatures as a backlink then you need to keep posting in related forums continuously, else over a period of time the backlink value gets discounted. In case of article directories, many articles of same niche gets posted continuously and you only need to do these submissions continuously for getting those freshness to your backlinks, better yet articles get approved over a period of 1 day to many months, so the backlink building also becomes natural.
I think forum comments is just for increasing backlinks, and blog/article making is good enough because you gain backlinks from a quality content site.