when we put comment in the dofollow blog post what is the most important for SEO, site PR value or that blog post PR value....
Basically it will be a combination of both. But i would have to say the specific page PR will weigh more than the overall site PR.
none of them, the most important question is: is the blog and blog post relevant to your niche, to the content of your website, yes or no.
Some say that PR is meaningless nowadays. Certainly that is what Google wants us to think. They are trying to stop the PR selling and PR driven link exchanges. IMO, PR still plays a role in ranking, but PR is a value given to a page, NOT to a site. If PR is meaningless, why does Google spend so much time encouraging the nofollow attribute? Bompa
You have to consider both. However, if your link is on PR page, that is worth more. whatever, if that is not related to your niche, I don't think you will be able to see difference in SERP, So, no use
relevance is the most important thing going. Google has indicated that it "almost" regrets PR- as it's become a trading tool for selling backlinks. Just make sure the blog in question is indexed by Google.
When you comment in dofollow blog is published, you will get a backlink from that particular page's PR value, not the domain. Important for SEO, is dofollow backlink, anchored keyword, low outbound links (both dofollow and nofollow), not a bad neighbourhood (not linking to any adult/gambling related sites) and from relevant contents.
When you will comment on a blog post it's ok if the blog have PR. It will be more profitable if you can find blog post page PR.
The single most important factor in blog commenting is the words per link ratio. If you comment on a pr10 page , that is super laser targeted relevant...but! If the words per link is low, the link value will be assumed to be low because of the net content benefit to link ratio. Content is king - It's mathematically proven to be so