I was always taught and told that a black radiator would shed heat more efficiently. The only reason I can think of on the newer ones is because they design them with better capacity/tolerances, ie., more tubes, etc. or they don't need the transfer because of lower horsepower? Copper/brass is actually far more efficient than aluminum at dissapating heat. Aluminum is only good because they can put more tubes in the core. But you are WAY better off if you can use a copper brass bigger radiator than aluminum. Just the laws of physics.