I have seen many mobile apps which currently use hamburger menu as sidebar menu as it is very convenient and user friendly. Now, we have started to use it in our mobile apps design and it is very important how should hamburger menu open.
In android mobile app of StackExchange, as well as in all Google apps, it slides out on the current page and behind it I am able to see where I am. On Facebook's android application, is pushes the content to the left. The opened part is flat and without shadow.
Which one is the right way to choose and which is the main distinction between these two approaches?