The difference of Plastic and metal in a variety of watch jewellery displays

In our mass production process , metal and plastic are improtant . what are they difference ??

1)the price of metal is expensive thand plastic .

2)plastic can reduce the labor hours 

3)Metal has speical lustrousness, opacity, ductility,Easy processing . the plastic can be with metallized effect too , but this effect can reach the same level of metal . so for high-end brand , we will use real metal .

4)Relatively speaking, plastic is not as hard, strong and rigid as metal.But plastic is more malleable, lighter and cheaper.