Fellow Photo-enthusiasts,
Choice of materials is only one aspect of good engineering. Which is best really depends on what your criteria for "best" is.
Then again, if your criteria is, say, survivability from a one meter fall onto a cement floor, then choice of material still is only one design parameter. In the case of a fall, damage does not depend on f=ma. The force on a body is relatively the same anywhere close to earth whether stationary or falling. The only time the force would be different would be if you are in space or on another planet. What is more of a concern is the difference of potential energy from a body at rest one meter from the ground to the potential energy from the same body at rest on the ground.
The basic law of physics says that energy must be conserved or rather the potential energy lost in the fall of a body must be converted into either heat, noise, or deformation of the material (this doesn't cover bouncing which would be converting the kinetic energy back to potential energy minus losses). Clearly, modern polycarbonate materials are more efficient at converting kinetic energy to heat or in effect absorbing the shock. Metal parts will tend to deform or transfer the energy. Again, either the energy causes the metal to bend or break or it is transfered to whatever is attached to the metal or it is returned to potential energy.
Survivability for a metal camera will depend on whether the transfer of energy can be dissapated by the rest of the non-metal parts or if the deformation itself, if any, causes the camera to malfunction. In the former case, the survivability will depend on the non-metal parts and metal parts inside the casing that are more fragile.
Ultimately, it is not cost effective to design a camera based on crash-survivability alone. Size and weight must also be considered. If they were not considered then the best camera to take an impact would be a massive sorbethane blob that would covert all kinetic energy to heat or massive metal exoskeleton that would deform but not transfer energy to the innards.
Obviously, the best camera has metal parts where you need 'em (where rigidity and wear are factors) and polycarbonate parts where it makes sense (size and weight, impact absorption, et al). All this in a package that isn't too expensive or made of unobtainium.
For those who have a look at the Aria, it is a beautifully engineered camera that is very compact and lightweight and mounts wonderful lenses.
Suggestion: don't drop your camera.