I prefer Facebook! In Facebook I can build my own targeted lists (custom audiences) and advertise to those people only. I can target my audience much easier with Facebook, I can also give more information on what they are getting if they click on my ad and the biggest reason I prefer Facebook: I can use images! A picture is worth a thousand words, you know
It depends on your business and your goals. Facebook works better as engagement tool. Besides, you can target people much better than in AdWords with such categories as age, education, interests, groups etc. Google is good to acknowledge people with your business, and then to use it for remarketing tasks. For big companies, Google AdWords together with Google MyBusiness is absolute must.
FB if you know exactly what your customer is, google is more for boarder group of people unless you're wiling to spend more to bid for the keyword. hope it helps.
It depends on your goals as some have mentioned. If you run a local business like a service station, hotel or restaurant you likely have customers on the go and not familiar with the area who would search for you using a search engine and not be looking for you on a social site.
It depends on business. Some good really good for FB and you can selling that only there. Like clothes or mobile games. But some things, like b2b things: services, complicated products and much more b2b you can promote only on Google
Facebook is great when it comes to targeting your audience and can be great for local businesses. There are so many users on Facebook that you can target, and if you know your audience, it's even better and can be cheap to reach them also. Google is a great platform as well but is expensive and you're competing for limited space with others. It all depends on the type of business you have and what your goal when it comes to promotion. If you're considering Facebook, Fit Small Business has a great Facebook Advertising guide. http://fitsmallbusiness.com/facebook-advertising/
I feel like Facebook is good for beginning but once you get big enough also include in google as it's a huge player in the advertisement scene. Facebook is definitely cheaper and easier to use but google if utilized correctly can become a game changer. I use both