Neither is better. They are quite different IMO. Facebook is much more about social connections and Twitter is more about information.
I think while Twitter started as a micro-blogging site where people answered the 'what are you doing' question, it has evolved into more of quick hits of information. Yes some can be quite mundane but most users have a general focus that they are tweeting about rather than just themselves. That is at least for the users I follow.
Twitter is absolutely self promotion but it is also amazing for breaking news.
If you want to reconnect with friends, chat, show photos then FB is the way to go.
Or be like everyone else in the world and have all of them.