Facebook is the best social media site to increase your website traffic.

FB is better but we should not forget Twitter also. Twitter provides right traffic and it if you do it in a good manner it would be a great way of traffic for you.

I think Facebook

Facebook is the best and more help to overall search engine ranking for a website

Twitter is not good as facebook

both are good. but in facebook there is no character limit so you can convey your message in a better way.