Google+, the smaller rival to Facebook, shows signs of gaining traction by exceeding 100 million users, but when those users log on to the social networking service they are spending less time at the site than previously.

Some observers would say that isn't good news, while others would point out the two services are vastly different in how people use them and how their companies are integrating them into their business models.

Google CEO Larry Page published a public letter recently in which he mentioned the increased user numbers. He also said the company's social network, which was introduced last summer, is now integrated with 120 services, including Search, YouTube, and Android.

At the same time, it was only a little more than a month ago when market analysis company ComScore reported figures indicating that Google+ users in January only spent on average a little more than three minutes at the site, which was down from December.

So what gives?

There are some indications Google+ may be making headway, although to be sure it's a far cry away from putting any dent into Facebook's numbers.

Experian Hitwise says U.S. visits to Google+ exceeded 61 million in March, up 27 percent from February, according to CNET, which also reported that Facebook's U.S. visits in March totaled 7 billion. While that’s an incredible number, it's actually down since July by 15 percent representing 1.3 billion lost visits, although those numbers don't include mobile visits to the site.

And speaking of numbers that don’t count, the Experian Hitwise numbers that indicate Google+ is growing only account for U.S. visits, which makes things interesting considering Google+ has a strong user base abroad. Nearly every day someone from outside the United States adds me to his or her circle. In comparison, that has only occasionally happened with my Facebook account.

Not only that, but comparing Google+ to Facebook feels a bit like an apples and oranges thing.

Anyone who has spent any time using either network can see they are vastly different in terms of how people use them.

While Facebook remains a place where people largely only associate with people they know, Google+, like Twitter, is where you’re more likely to engage with strangers. As a result, on Google+ you’re less likely to hear personal news such as "Junior got an A on his math test" or "I just ran five miles" and more likely to see posts commenting on news or photos or videos that aim to make a point and influence people’s thinking or behavior.

Another important consideration is that the numbers that often get thrown around about the growth of Google+ often don’t include visits from mobile devices or traffic driven by the Google+ notification bar. That means without even going into Google+ you can see who’s giving your posts +1s, commenting on them, or adding you to circles.

It’s a number-crunching game that can be tricky to understand.

Google+ has some devoted users who don’t really much care that the masses haven't jumped Facebook’s ship. If they do, the Google+ experience may become more like Facebook's and that's not something that some people want to see happen.

Follow Christina on Twitter and Google+ for even more tech news and commentary and follow Today@PCWorld on Twitter, too.