PR is important, but definitely overated. PR absolutely matters to link partners, and it matters a little to Google even…PR is an approximation of your site’s strength, however it doesn’t mean a thing if your site isn’t optimized for the keywords you are gunning for. However, if your PR5 site is optimized in exactly the same manner as a PR4 site, you can bet the PR5 site will rank higher. Really, once you cross the PR5 threshhold, PR basically doesn’t matter as much anymore, since you will have a pretty strong site. At this point it all comes down to on and off-page optimization to gain SERPs.