It is your own personal preference. For me, I don't feel I have a large enough viewer base at the moment for Facebook. Twitter is enough to shoot the video out and because I used hashtags and words that people search for when I post my video, my video is seen more from there because people who search up a keyword can see the video pop up and then retweet or whatever. Much more useful when Facebook doesn't do that. Later on, I might implement Facebook as more of a community thing.