For whatever material construction your flavorizer bar is made up of, either of them is exposed to extreme temperature conditions which could degrade them over time. However, their life span differs from each other so also is their ability to conduct heat. Your Flavorizer bar either comes as a stainless steel or porcelain enamel steel.
Although both of them are excellent conductors of heat, however, in terms of Performance, the porcelain grate can grill faster ue to its inherent ability to retain heat. One thing to note is the porcelain enameled grate are pieces of cast iron metals with a coating of porcelain. However, the porcelain grate gets corrosive for a short period. While the stainless steel grates have extreme durability, it does not attract heat like the porcelain enameled grate.