Weber makes three varieties of cooking grates. Stainless steel, porcelain enameled cast-iron & porcelain enameled steel. All three varieties are easy to clean, durable, and will produce great sear marks.
Porcelain-enameled steel cooking grates - Easy to clean and are great basic style grates.
Porcelain-enameled cast iron - Retain heat better and longer
Stainless steel cooking grates - Can last for a very long time if they are properly maintained.