What you will prefer and why ? Backlink from relevant and unique conetnt with no PR OR Backlink from Hight PR unique but irrelevant content. Which is more valuable and why ?
Ofcourse Backlink from Hight PR unique but irrelevant content. For a Search Engine a Link is a Link no matter whether it is relevant or not. Link from a High PR site always increases your credibility!
I do both. After I started commenting on non-related sites, my ranking jumped up. I think it looks more natural.
A single one-way link from a high PR relevant site will do wonders for your PR and SERP. However, I recently purchased a very enlightening report on another forum that spoke about the value of getting many one-way links from all the pages of a single website or blog. The most revealing aspect of the report was the fact that when these links are sent to an article, it seems to get better results from Google, than if they are sent directly to a top level domain. Further credence was added by the fact that a very popular article marketer who boast about making $14,000 from one article, simply neglected to tell his readers who purchased his report, that the reason for the popularity of that article is the fact that he is paying for over 23,000 one-way links to the article from a totally unrelated website. Under those circumstances, 1000's of one-way links from an irrelevant site ( I checked it personally) worked for him.