I have and carry both a Blackberry for work, and an iPhone because I wanted something that wasn't under the control of IT overlords.
I'm sure that I'm not the only one who carries a Blackberry in the default plastic holster and drops it onto the floor at least once every few weeks... and it's got nothing to protect it from that dive.
My iPhone, however, being my personal property, does get better care. It's usually in a case in a pocket, and only small portions of its surface are directly exposed...
I'm not surprised that iPhones fail less. People take far better care of them.