Google will win. No doubt in my mind. Not only does the company name help, but look at what happened to MySpace when Facebook arrived.
I wouldn't be so sure. First, the name thing doesn't necessarily help Google. A lot of people, myself included, get a little skeptical about putting too much of our information and trust in a single large company. I use Gmail and Google apps and have an Android phone...that might be enough for me and quite a few others. Also, Microsoft was the really big name trying to compete with the (then) relatively small Google. Microsoft got crushed by them because Google was very, very good at search. Facebook is very, very good at social media.
As to MySpace, they were one of the first big players in the that space. That's not always a good thing. Facebook came along and did a lot of the things right that MySpace did wrong. In effect, they learned from MySpace and then did things better. I've played with Google+ and it's nice. But not as good as Facebook at the moment so Google doesn't have that going for them. Also, the number of people on social media was fairly small with the MySpace craze (at least compared to today) and it was brand new so people hadn't really pledged allegiances yet. Again, that's not the case today. Facebook has 100's of millions of users and a pretty faithful following.
Lastly, there have been some great articles about how Google's DNA just will not enable it to compete in the social media space. Much the same way Microsoft has not been able to compete in the search space - it's just not who they are.