Facebook is old, that's why they are popular but Google+ is new. Google+ could be more popular then Facebook one day.
For your publicity, it's always better to go as much as you can. As others are telling, why not going for both when they are free!!
I think Google+ is better more than face book and i think face book is time wasting web site for all Business mans.
Facebook is a great social networking site. And Google plus is come from a great search engine site. So that it is difficult to find out which is best?
True That! But if you are really willing to be in good search engine rankings of Google than you should market more on G+ as compared to Facebook, as you can get quicker backlinks via G+, but if you are really willing to use social sites for marketing as well as for your entertainment purposes than Facebook is most preferrable, and like you said "G+" needs to go along way even to become equal to the reputation of Facebook!
Google+ is really poor but they kind of have anyone in SEO over a barrel in that we need to use it. Facebook in terms of usability wins hands down but google+ will only get more and more important (not that your average Joe on the street will use it but more web developers will)
Google is doing now bit spam... because google + is now influencing the search results of google.. and faceook is always a fabulous social site...