You can compare the same parts on any two vehicles made by the same manufacturer, or even different manufacturer's and find many differences. Headlight assemblies are made by five (5) different suppliers (the last I knew) within the U.S. and then there are the imports. Oddly enough there is a difference in the polymers used to make these plastic parts. There are clear polymers out there which would NOT degrade over the average lifetime of a vehicle but they would add pennies to the cost of the product. Auto manufacturer's bean-counters look at this as "how much would it cost for 100,000 of these units" and "how much can I save using a cheaper product"? It's all about the money and the bottom line--profits.