I think Facebook is pretty good as everyone uses it and its a great way to showcase your work and let people know what treatments/offers you are doing on a day to day basis, websites IMO are great but people will only go on your site if they previously know about you and probably won't take a look through it really regularly - apart from if you are really well establishes or have celebrity status!
Also its free, so while you are setting up you don't need costly website fees but you could think about it when you are more stablishes. Websites do look more professional but its getting people to view it, you could put a link on your FB page to your website if you really wanted, that would increase the hits on it x