While there are a few success stories of businesses who have foregone a website in favour of using Facebook, in reality this is quite rare.
It’s very unlikely that potential customers will simply stumble across your Facebook page through a search engine. Generally, they need to either know your Facebook address or find it virally, such as via Facebook itself.
With a website, potential customers don’t have to search for YOU; they only need to search for WHAT YOU DO.
A website can be optimised for search engines, meaning that on a website you can write your own page titles and page descriptions, control the page design and submit a sitemap to search engines. None of this is possible on your Facebook page.
Facebook certainly offers a great way to communicate directly with current and potential customers, but that is its main purpose. A website offers that and much, much more thus you should consider using Facebook to compliment your website when planning your online marketing strategy.