It is all about physics and how it lands. Even a good case can do no more that keep the glass fragments from scattering if it falls just right. A good case with lots of padding on all edges and corners will increase you survival chances greatly but there are no guarantees.
A good screen (Glass) protector with a case will help. Some use these, some think they are invincible to damage/drops, keeping it nude, then one day they have an accident, and wa-la.