i think it depends on your demographic target market.. facebook will more relevant and flexible to choice your target market than Adwords CMIIW
The best way for all is try, try and try and you will see, many people can tell you the personal experience, but your experience is the most important, try! It is cheap
try both of them, but first begin with Adwords, it is more common, anyway, you can always compare which advertising is more effective
Google Adwords is more targeted toward a product. Meaning that people looking such product will more likely go to your site. Facebook is targeting a demographic audience. You are hoping that your target market will see something they like and buy from your site. My opinion is that Adwords is best but try them both out and see what performs better.
I would go with facebook. If you ask me the same question a year or two ago the answer would have been google adwords. Facebook has as much traffic as google. Plus the targeting is better with facebook. The rules with facebook are not as strict. Google shutdown 30,000 accounts within the past year. Google doesn't like us marketers. So Facebook all the way.
I'm a fan of both. You can get low priced targeted clicks with Adwords and Facebook is good for targeted low cost per impressions. Facebook is much easier and faster for ad approval.