iOS devices - innovation and reliability

Besides innovation (which Apple established with the first iPhone, but isn't maintaining on most fronts), reliability is the hallmark of iOS devices.  Am experiencing Adobe Reader plugin hanging my entire work Windows XP computer.  Why?  Probably some combination of Firefox version, Reader plugin version, OS version, and hardware.  Apple controls most of the h/w and s/w stack in their products and thus there are far fewer variables to manage.  Hence greater reliability.  It's not magic or some sort of Apple brilliance.