(The interface also invites having a "loudmouth" circle with zero notification level, so you can follow people without having their posts in your default stream).
Otherwise, G+ Circles are ridiculously clunky and slow, due to Google choosing superficial eye-candy over functionality.
The fact that Google+ prioritizes and emphasizes splitting friends into these circles as a PRIMARY means of organizing your friends is a huge difference. Although it is cumbersome, it is a much more realistic representation of human interaction, making friends and having different groups of friends.
Almost all my extended global family uses Facebook several times a day (we have a closed group), and I often sit next to other family members using the system. I am much more familiar with it than most people, especially with non-expert users.
It does require some effort to sort Facebook friends into half a dozen channels, but Facebook suggests people to add, which actually makes it rather easy. It becomes a natural progression, over time.
Meanwhile, whatever the theoretical claims, G+ remains almost completely unusable. In my experience, it's virtually impossible to get ordinary people to use it, and they don't last more than a day or two. And from a usability point of view, Circles are crap.
Although I've used G+ quite a lot, and have something over 5,000 followers, my use has declined over time. Following the last desperate (Facebook copying) redesign, I've more or less given in...
I think none of the networks are perfect, but I don't use Google+ only for personal connections. There is quite a lot of (photographic and technology, at least) content that is interesting to read.
And not to get into any sort of Fanboy war, but which redesign are you talking about? Before Google+'s most recent redesign into the multi-column pinterest-esque layout, Facebook's timeline update is in fact quite a copy of Google+'s old design (bigger pictures in speech bubbly things out of profile pictures).
I've lived in North America and my wife's family is Chinese so we are pretty widely spread. I have close relations in five different countries, but the majority are in Asia.
So, in an average Facebook session, I see posts from about 50 people, and I know almost all of them very well. I see a lot of baby and toddler pictures, with more to come ;-)
I have no relatives at all who use G+, and very few colleagues/business contacts who actually use it. Also, I don't see much new content there. I've usually seen it already via Twitter, Reddit, HN or RSS feeds.
I also use LinkedIn and Quora, and as a former /. and Digg user, I sometimes drop by those as well. They all have their niches. Unfortunately, it's hard to see anything that G+ does better than the rest, from my point of view.
Also, Hangouts is probably the biggest unique thing for Google+. By far the best web-based, free, multi-person video chatting experience IMHO. Not to mention it can be tremendously productive if need be, with in-window document editing and screensharing. It's somewhat based on the video conferencing solution that Google has been using internally for remoting into meetings for a long time.
I agree about Hangouts but it's a non-starter when none of my family is using G+. They use Facebook chat, Facebook group chat, and Skype. Hardly any of them use Gmail, so my chances of moving 30-odd people to G+ are basically zero....
With consumers, technology is a relatively small part of technology choices, and inertia is a huge factor.