What is the best BBQ cooking surface?

Cast Iron is used in most BBQ's, with a range in quality available. Premium cast iron surfaces can be coated in a non-rust ceramic finish that prevents rust and is easier to clean.

Stainless steel cooking surfaces are also available. In many of the later models the grills come in stainless steel. Stainless steel is ideal if your BBQ is to be situated near the beach, as a stainless steel finish will resisit rusting and erosion due to the salty atmosphere to the greatest degree.

Source: The Barbecues Buyers Guide