Facebook is sort of awkward. It doesn't aggregate information like I like. When online, I want floods of information and opinion. I can look at facebook for a few minutes. "Yes, that's a cute baby. Yes, that's a bible quote." If I wanted that, I'd go outside and talk to people. Relationships are more suited to the slower flow of real life. On twitter, I can see conversations about manga, etsy, the state of black America, tv shows...ALL AT ONCE. Updated constantly. Sometimes I get licensing information IN REAL TIME! Real life and facebook are more of a mixed bag. You're thrown in together with people you don't really choose- former church members, old coworkers, schoolmates, family members, and what they talk about may or may not be interesting.
I like the choice of twitter. If I end up with a religious fundamentalist on my twitter, I can merely click unfollow. On facebook, I end up with a lot of folks like that on there as not to offend.