Selected answers from the Dumb SEO Questions Facebook & G+ community.
Clement Low: I think factors you may have to take consideration is are the PR real. Furthermore PR had not been updated for more then half a year, so what you see may not be what you get.
Steven Ciccantelli: +mitch wilson make sure its relevant and I am very new to SEO and link building but I would take a valid PR 5 aged site over The four PR 3 any day of the week.Wait until someone smarter chimes in before you take my advice tho.
I would first look for the relevant and quality link rather than the quantity. Domain Authority and age are another valuable metrics in determining link popularity. ;
Steven Ciccantelli: +Ranu Jain tho its kinda funny I have a ,PR 5 that at times gives more juice than PR6 and a PR7 lol how can someone actually keep up....then once I get a grasp..Google changes its mind.
Matt Raynes: Steven and Ranu are right, go for relevancy and quality. ;Also, consider how many existing external links exist on the page. ;Too many will dilute the link value you'll be acquiring. ;
Simon Fryer: +mitch wilson ;forget about toolbar PR.
The Moz toolbar will provide much better metrics, such as PA, DA, MOZrank and MOZtrust to evaluate a page's link value.
One thing no-one has mentioned is where the link would be placed. This is crucial. ;
That said, relevance is the real key. You need to assess the semantic value of a link in addition popularity-based link metrics. Hummingbird anyone?
Micah Fisher-Kirshner: Created a formula back in the day for this, basically just ask yourself what impacts PR and create a formula from that, thus:
What is the mathematical difference between PR 3, PR 4, PR 5, etc? What is the mathematical difference between having 1 link on a page vs 50? What other factors play into the value of the link I'm getting and what mathematical formula can I reasonably make out of that?
Now, whether you should still be using PR as the sole factor or value for determining the worthiness of a link is another story :)
Nauman Tayyab: Well simple answer is if PR3 site is relative to your site , than it is more strong or valuable than PR5 back link, relevancy is also very important
Greg Kristan: +Nauman Tayyab ;could not of said it any better!
Micah Fisher-Kirshner: +Nauman Tayyab: That's too simplistic of a view. Would you turn down a PR 10 (let's say New York Times) link vs a PR 3 relevant site? Probably not...
Greg Kristan: I think PageRank might be going away. Google has not updated it a good amount of time and Matt Cutts said don't expect an update this year. ;
I know for myself if I could get a link from a relevant site that would actually bring in qualified visitors to my site rather then just visits I would actually then choose the relevant PR 3 site
W.E. Jonk: From the expert panel in this weeks SEO Questions hangout on air on 00:45:01 into the YouTube video: https://dumbseoquestions.com/q/would_four_pr3_backlinks_be_better_than_one_pr5_backlink
Would four PR3 backlinks be better than one PR5 backlink? 
