Fan pages are visible to even those without a Facebook profile account. If you send a Twitter message or email with a link, anyone can view the page.
Fan pages are indexed outside of Facebook. Meaning, if someone does an online search of your company, this is one more link that will come up.
Not sure who your target market is? Facebook fan pages can help you figure that out. Each page keeps statistics of who your followers are and who is participating. It will tell you if they are male or female, their age range, where they are located and what language they speak.
With a regular Facebook profile you are limited to 5,000 friends. With a Facebook Fan Page the number of fans is unlimited. This might not be a huge thing if you are just starting out, but always plan for your growth.
You can further establish your brand. People do business with people they trust. Social media is all about building the trust over time and Facebook is a great way to do that.