I like Facebook’s feature “True Friends” because it allows you to have an open, public space for the people in your list that are just acquintainces and another private, more personal profile for those you know you can really trust. I feel this makes Facebook emphasize a little bit more on deep, personal connections, rather than just competing for the most connections (as may happen on Twitter). Also I think Facebook’s interface of everything-in-a-click IM, messages, videos, photos, etc. give it a great advantage, Twitter might focus a little bit more on the interface design, because even though Facebook is more complex it is actually easier to use for many users.