It's not that it's not accurate, it's that the PR that you see in the toolbar (or any of the PR checking tools) is only updated 3 or 4 times per year, but PR is actually calculated continuously. So, sometimes the PR you see is out of date.
Well it depends on the content and relevancy to your site. If the PR 5 is not related to your site, then i would go with a bunch of PR 0 in hopes that some of them are relevant. Its all about your link in context.