Though facebook is strongly holding its users, But google + i also good enough to give some competition
I'm on team Facebook. Maybe it's because majority of my contacts are on FB, and only a few have engaged to Google+
Facebook began to lose a few due to the updates that I had on its interface. Many users didn't & still do not like them. Same went for Myspace. They lost a lot of users eventually almost all now due to the changes that it had. Anyways I don't remember what website, TODAY, I saw a chart on how Google+ got to the million people in just less than like 18 days I believe it said, way faster than Facebook & Twitter which it took them almost a whole year. ( For both, Twitter got to a million faster than FB)
Google + is still in its initial stage i'd say. The interface is not very enticing, features are not very handy. We might have to wait to see the full turn.
Google are a search giant, they will find it difficult both because of thier incumbency in search, and the general brand affiliations. They are like Microsoft to IT, where Apple is to Design. Facebook will maintain its foothold.
For me both have different use, most people take both in one sense which is not correct for me, Google is typically a search engine and typical business application for business users also facebook have business application with his social uses, but you can't depend on one for your business.
I have been using facebook since 2006. But now i am using Google + 5 few days ago. I think google+ is better than Facebook at this time.