Since I have been involved with Japanese commuters bike the differences of fender material in my opinion goes this way :
If you want the looks and durability I go for the stainless fenders. For utility and stay-in alignment the plastic fenders got it. The aluminum fenders advantage is lightness but easily deforms. Bridgestone, National, Panasonic and high end commuters bike are usually with plastic fenders. OGK plastic fenders are usually use on other brands probably for lower costing. Steel fenders on the other hand specially the ones used on vintage and classic bike are very stable to dents due to thickness.

In places where you have rains the plastic and stainless fenders is very adaptable and rust free. Steel fenders coming in the market are thin and prone to dents. In any case, all fenders staying looks and lasting depends on the user's maintenance habit and use.