Twitter lacks intimacy...
On facebook, if you post something, there can be a whole conversation afterwords in the comments section of that post.
On twitter you are just making @blahblah posts on your page to talk to someone else. You dont even know someone replied to you unless you are constantly checking the "Mentions" page.
Facebook seems to offer more than Twitter. I don't want to just write 50 words about my day. I would rather communicate with people that I want to communicate with.
Twitter all the way. Facebook is too drama-like, especially in high school. It's also kind of dumb to me because I feel like Everyone I know in life sees what I put. On Twitter, adults don't follow me and it's only people who actually care that see what I put. It's so much different and it's so simple. Simplicity is a big thing for me.
I prefer Facebook since it is easier to find and view photo albums, and there are games, apps, pages, music band pages, and a lot to do on Facebook while on Twitter you have to click links on people's tweets to view content on their site in many cases.