nowadays, in Iran most of the people prefer to use Instagram instead of Facebook. what about your country? which one is more popular and why?
In the UK, most people prefer Facebook as it has more possibilities. Instagram is limited to video/photo, whereas Facebook's posts can just be text, photo, video, link, etc. Facebook also has better posting systems. more features, better User Interface, Better cross platform support (PC, Windows Phone, OS X, iPhone, Android etc.) Also the biggest win is that FB has more users and has been around longer than IG.
I think facebook is more useful and its providing other facilities also like advertising. and Instagram is only for pics and videos but in facebook you can share everything and can create your own business page. In short, I prefer the facebook.
Depends on the use really. In the UK, Facebook still tops but in the image community Instagram probably trumps Pinterest. Furthermore, there are specific threads on Google Plus for getting images out there. The point is, we're in an age of social media choice at the moment. Why stop at just one network?