I think both platform has their different usage. If you want to search for something on the net, Google is a good choice as they provide the most relevant searches pertaining to what you are searching for. Facebook is more of a social network where you connect with friends, colleagues etc. You use Facebook to interact with them and sometimes, you can even find your long lost friend on Facebook and get in touch. It all depends on what you want to do in the first place.
You know, after the introduction of Google Play as a new image of Android Market, I have lost the last doubts about Google's world conquer being unstoppable
i think they are completely different although both of them have nearly the same traffic but facebook should be a little bit easy to use because we can target specific audience