Soft-feel plastic, wooden or aluminium case for iPhone?

Which would be the safest option if I were to drop the phone for example?

Based from experience the plastic and aluminum case worked best in protecting my iPhone from unexpected drops.

Why would you want a case that is similar in material to the casing of the actual phone? You want something that is shock absorbant, something that facilitates impact damage, which shouldn't be anything metallic or wooden. These materials will crack or break regardless of whether this protects your phone.