A two row aluminum radiator (with larger 1" or better yet 1.25" tubes and more cooling fins) will cool more efficiently than a 3 or 4 row copper/brass radiator.
Most of the older design copper/brass radiators have smaller diameter (3/8-1/2") cooling tubes and less fins, with the fins running parallel to one another.
In modern aluminum radiators, you not only save weight over copper/brass, but the tubes flow more coolant and the fins are diagonals which provide more cooling surface.
I know that this isn't specific to what you asked, but there is a point with a copper/brass radiator that you just can't get it to perform much better. The thickness of the copper/brass hinders cool air from passing through it, particularly when it is clogged with debris or hindered by an a/c condenser in front of it. The cooling tubes on the engine side of the copper/brass radiator do not benefit from the cooler air exchange.
Check with GRIFFIN, BE COOL, RON DAVIS RADIATOR and PRC. The cost of an aluminum radiator is more than a copper/brass, but with the demands on todays cooling systems the old copper/brass just cannot do as much as we'd like them to do.