On-screen navigation buttons offer many distinct advantages over physical buttons—they can change orientation along with your device, they’re capable of visually morphing to indicate secondary functionality, and the user experience is more consistent when buttons and app elements require the same amount of force to press. Add to that the fact that they’re far less likely to fail and can be themed or even switched out altogether, and it’s hard to come up with an argument in favor of physical buttons at all.
Really, the lone knock against on-screen buttons is that they occupy precious screen… more
Sig Nordal 