Yes.. Facebook is more reliable than Google Plus. but if you are optimizing webpage for Search Engine, then Google+ will help you.
since facebook is widely used and it contains plenty of users,dominating the social media services and user friendly and ease to use
At a certain point, it was required to have a Google+ account together with your Google account. I now have a Google+ and never use it. I think this is the same for most Google users. The power (and size) of Facebook is too big for Google to take over. However, Facebook is getting bad in terms of Vines in my timeline and many more nonsense. When Google can come with a better alternative, that could make a difference.
facebook contains lot of users account being used by plenty of users for various purposes,plays a vital role to promote the brand and to drive traffic thats why i go for facebook
since facebook is widespreadly used by lot of people for various purposes more chance of getting fans/followers would be on facebook which directly leds to promote the site and to drive traffic
Well, I think the main problem is Facebook comes first from Google +. So Google + needs some more time to became users favorite website. And we can see that Google + providing more same services like Facebook already have. So I think that in coming days Google + will do fight with Facebook to take the no 1 spot in "Top Social Networking Sites".