Both are best. Social networking sites are gaining key part of traffic so market yourself on as much sites you can.
I like Google+ because it presents a more sophisticated atmosphere and the security is way better than Facebook's. Plus most people use their real names.
It will improve your SEO. Facebook Vs. Google+ depends on how many friends you have in each of those networks and how they respond to your posts.
For SEO, you need to share all your networks together. Would prefer you to made your niche in both the social networks & share it on fb as well as google+.
Google + will help in website ranking as its the Google's product, it will definitely help your website ranking on Google. Facebook is a better source for web traffic as it is used by more users around the globe, a lot more than Google+.
i think Google+ is more Powerful than face book and i think face book is time wasting website for All Businessman's.
I don't think that G+ is more powerful than FB. but for promotion and SMO it is and ideal social network