I have to go with Facebook on this one.. Also, to add if in theory that anyone were to succeed over Facebook, I am not really sure Google+ is going to be that kind of giant. So far I have seen more promising social interactions with Twitter... which leaves me to definitely wonder what Google+ is going to do to really step their game up. Only my opinion of course
Its too early to decide which is more powerful. Obviously Google+ is much smaller than Facebook at the moment but don't forget, its been there for just few months. And already it has grown enormously, thanks to the rock solid backing of Brand Google. But we still need to wait 2-3 years to get an idea which one's going to rule in the years to come.
Google plus will help to get website ranking ? but if we talking about more traffic facebook is good source to get more traffic for your website.