Excerpt from a timely Google+ reality check
In fact, Mahmood and Desmedt say that the features on Google+ are merely a subset of those that are available on Facebook. However, they concede that Google+ has a better interface and that it allows finer control of content through features such as disabling the resharing of content and in allowing users to edit content by modifying or backtracking on their comments at any time. These are things that are not possible on Facebook.
Finally, they say that while Facebook uses an encrypted channel for login, Google+ uses it for the entire connection. That makes it harder to carry out a man-in-the-middle attack on Google+.
Overall, Mahmood and Desmedt don't appear to have identified any showstoppers in their analysis. Google may want to tweak a few things such as the sharing of metadata and the ability to make exceptions when sharing content.