On-Screen or Physical Buttons On Smartphones

When I refer to buttons, I am referencing the three common buttons located on the button bezel of many Android smartphones (example below Samsung Galaxy S5):

Android smartphones have been making a shift towards purely on-screen buttons, leaving the bottom bezel of the phone empty, for example Google's Pixel:

Apple on the other has not followed suit, and continues to use a physical home button on their iPhones, even their most recent iPhone 7:

Why is Android going on-screen, while Apple is still keeping physical? What are the advantages and disadvantages of both?

My current thinking is that Apple's iPhone has become iconic for having the home button, and that by removing it they move away from the core visual style of their previous phones. By continuing to have the home button, Apple phones can be even more distinguishable, even more so with Android removing physical buttons.