Both plays a vital role for getting a higher PR. Number of quality backlinks I think have more value then content. Google has not updated PR for a while now. People saying Google is putting more emphasis on content now considering widespread use of buying links to get high PR.
PR has ONLY to do with number and quality of backlinks and has NOTHING to do with content whatsoever... Your website can distribute the gained PR from backlinks in different formats so the internal PR flow of your website can be influenced by the linkingstructure of your website, but the PR itself ONLY and ONLY comes from backlinks from other sites to yours.
PR comes only from quality and quantity of the backlinks you have. Also, it depends on the ratio of Inbound to Outbound links from your site. Thanks, Cybotrix