Although both are the best site, I really like most Google+. Obviously, it is a best site of Google. Undoubtedly you can choose it if you want a plenty of traffic. It will really help you to promote your site. If you have a Google+ page then Google gives more priority to such website. I think it is a brother of Google.
i fell that Google+ and Facebook both are very good site but Facebook is far more popular than Google+
Hm, I don't know why everyone here says Google+ is better, I myself have never used it neither I plan to do so in close future because all of my friends are on Facebook... That's pretty simple reason; What do I expect from an social network is to give me opportunity to be social. Simple enough...
Google+ is best for getting traffic if you want to sell your brands, then Google + is the best. Facebook is just for pagebook fan's like. It will not increase traffic.