One is the largest social network in history that has recently been making inroads into the search engine market. The other is part of the largest search engine in history and has recently been making inroads into the social media market. 
We're talking about Facebook and Google+, the No. 1 and No. 2 social networking sites in the world as of 2013. But from a marketer's standpoint, which one is more important?
Traffic
Facebook has well over a billion users, with at least 700 million of those users being active on the site each month. Google+ is about half that size, with over 500 million accounts and more than 350 million active monthly users. Though smaller than Facebook, that still makes Google+ the second-biggest social networking site in the world, despite being only two years old.
Facebook's active users still spend much more time on the site. Facebook users spend over six hours per month on the site, while users spend only six minutes on Google+. According to Time magazine, Facebook's time-spent figures are on the decline. On the other hand, Google's figures are rising.
Advertising
Google currently does not allow advertising on Google+. However, Google itself dominates the world of online advertising. It can use information about Google+ users when serving up ads all across its huge advertising network.
Facebook has both display advertising and "sponsored stories," which appear within the News Feed. It also allows users to promote their own posts so that they are seen by more people.
The most important difference between Facebook and Google advertising, though, is the purpose of the websites themselves. Facebook users do not typically go on the site with the intent to buy anything. With Google, shopping is often the reason why people visit the site. Click-through rates are therefore much higher with Google ads.
Since Facebook's strength is social connections and time spent on the site, it makes more sense for campaigns aimed at brand-building and improving customer engagement.
SEO
Social media links, followers and likes can have a big influence on local search engine rankings.
Google+ would seem to have the advantage here, as Google is sure to prefer its own social network when calculating influence. Most Google+ users stay signed in when searching the web, allowing Google to give personalized search results based partly on Google+ connections and the "+1" recommendations of friends. Google+ profiles are also a factor in calculating AuthorRank, which further affects SEO.
On the other hand, Facebook's Graph Search gives personalized results based almost entirely on Facebook connections and interactions. Facebook is partnered with Bing for these searches, so there is the possibility that Bing's search algorithms may give Facebook links and "like" recommendations more weight.
Facebook and Google+ both have their strengths. Whether one is more important than the other depends largely on the specifics of your business. For example, consumer brands with large or enthusiastic fan bases will likely do well on Facebook, while companies that get most of their business from search traffic should spend more effort on Google+.
At this point, though, both are too big to ignore. It may make sense to focus more on one of them, but both Facebook and Google+ should be included in your online marketing plan.
* Image courtesy of freedigitalphotos.net
