Aluminum's conductivity is 3 times that of cast iron and over 15 times that of stainless steel.
GrillGrates conduct heat more efficiently and more evenly. The hottest part of the GrillGrate is the cooking rail as heat is conducted up and through the grate.
The conductivity of the GrillGrate panels and the radiant heat (infrared) they generate is the reason why they grill food so much better.
Should we give Ian an A?