I think that for now Facebook is more efficient because more and more individuals are there than on Google+ for now. But this does not mean that it's going to stay like this. Google+ is Google after all and it's excellent to have that in thoughts.
Facebook has worked like wonders for me but I would suggest you to go with both as you will get more reach. Also, I have noticed that G+ isn't that strict when it comes to banning of multiple profiles, as regards to FB.
In terms of customer interaction and popularity I would settle to Facebook as it is more effective and giving us great leads compare to Googleplus. However, for SEO purposes probably you need to consider GooglePlus but if it's about promoting, customer interaction and more then Facebook should be my priority.