Given two radiators of identical design, an aluminum one would cool (transfer heat) better than brass, since the thermal conductivity of aluminum is better than brass.

The question that manufacturers were faced with was “How can a radiator be built with increased tube width, increased tube wall thickness and still end up being lightweight?”. The answer – ALUMINUM! An aluminum radiator built with 1″ wide tubes with a .016″ tube wall turned out to be approximately 60% lighter than the same copper brass radiator. The 1″ tube increased direct tube – to-fin contact and cooling capacity by roughly 25%. Therefore, a 2-row aluminum radiator with 1″
tubes is equivalent to a 5-row copper brass radiator with 1/2″ tubes. The state of the art engineering advantages of the increased tube-to-fin contact are far superior to the lead joint found on copper brass radiators. The welded aluminum construction also proved to be stronger than the lead – soldered copper brass radiator. Today all vehicle manufacturers incorporate aluminum radiators with wide tubes in their designs. GM, for instance, offers an aluminum radiator with 1-1/4″ tubes. Mercedes Benz uses 1 1/2″ tubes.