The cast brass and cast stainless steel burners have the smallest burrs — by far. This will mean less chaos in the gas flow, fewer trapped particulate matter in the burner and a cleaner burning grill. The following comparison shows how the ports are formed.
Why is port formation important? Several reasons. If the hole is punched into a sheet metal burner, it leaves a large tab inside the burner that will cause more chaos while burning. It is more apt to hold trapped food particles and grease, and is therefore more likely to burn through. (Note the Alfresco burner photo below.)
Molded ports in cast burners seem like they would be a good idea, but there is considerable difficulty in making them uniform. Thus, it is quicker and less expensive to drill.
Drilled ports are the most uniform and the most precisely placed. They tend to leave a burr on the inside of the burner, which is more noticeable (oddly enough) in a sheet metal burner. Cast burners tend to have smaller burrs.
Fire Magic grill burner has drilled orifices
Notice (from the photo on our site) the lack of extensive burring, allowing for a smooth flow of gas. Cast stainless...