I would definitely go with FB pages. Pages have the main features that a group would have but as the post above me says, it's much more customizable.
This might not be as big a deal to some people, but I think pages just look better than groups. More professional if you will.
Page is better because if you choose group, facebook may take the ownership from you if it gets popular.
With a page you have more freedom to create and customize it according to your business needs. So definately Page!
i just make both groups and pages... groups to get more people in and send newsletters! but pages to promote the link on google