it depends on your business, but I think Facebook will get you QUALITY traffic. You have to create an interesting facebook page or app and hope that it becomes 'viral'
create a facebook fan page and market targeted facebook users to Like your fan page. Eventually this will give you good result but Money wise it will cost you a lot lol
facebook: try to make a fb fan page... you can also drive traffic using twitterfeed,make auto update from your site, you can use to both fb and twitter
I suggest to use both twitter and facebook. A fanpage on facebook. Talk about your niche on twitter and connect your twitter to your facebook account. Start following people in your niche. Replying and retweeting to their topics as well as using #hastags will get your name out there fast.
use face book create pages regarding of your business Titles ,after than connect twitter connection in all face book profile and with other pages for micro blogging , you spend your time only for micro blogging on twitter these will be also appear in both