I’m pretty happy with both of them. They both have their uses.
Facebook keeps me in touch with family members I rarely get to see (I have a large family that’s spread throughout the entire continent of America).
I also use Facebook for my book club – we send out notices of upcoming books, and I suppose an email mailing list could do the same, but with the FB Group we also can post relevant articles or share websites of interest, post necessary contact info, and keep a running list of books we’ve read.
The third thing I like FB for is that I can share an issue or news item with my family and friends. Sure, I could email them all, but I find it intrusive and annoying when people do that to me. This way, they read my message if they read their news feed, and if they’re interested they can do something about it, and if they’re not interested they can ignore it.
Twitter I use for an organization I’m involved with. I follow other users who post about relevant things, and I post my own things about the organization. There’s no other way I’d be able to keep on top of the issues my organization is involved in. Some of the users I follow also have blogs I could subscribe to or newsletters, but not all of them do. Sharing of news and info – it’s amazing.
I don’t really get why people use it for themselves, as individuals, though. Tweeting about what show you’re watching or what you ate for dinner… who cares? All that stuff would be better suited to a profile page somewhere (like FB or a google profile, etc.).