Sabine Lenz, PaperSpecs, highlighted a great piece by Michelle Gabrielle Centamore, published in March/April 2008 edition of Paper & Packaging. Read "To FSC or SFI? That is the Question;" the comparisons and pros/cons of one certification over the other are really helpful! Here is a snippet from the article:
As companies seek greater opportunities to grow their business, but not at the expense of the environment, the demand for suppliers who invest in more sustainable practices is rapidly increasing. Certification offers reassurance that trees, for example, are being harvested responsibly, that land-use is being closely monitored and that across the board, best-practices in management and environmental stewardship are priority. There are numerous paper and forest certification organizations throughout the world. Several that are becoming prominent in the United States are the internationally recognized Forest Stewardship Council (FSC) and the Sustainable Forest Initiative, Inc. (SFI), which is a member of international forest certification group, Programme for the Endorsement of Forest Certification (PEFC). Although forest preservation is a priority to both organizations, their fundamental goals and backgrounds vary, thus the decision to favor one program over another may be based on a company's individual needs and preferences rather than attempting to ascertain if one organization is truly that much better than the other.
You can download a PDF of the article from a link at the end of the piece on PaperSpecs.