Copper-brass is more efficient for the same thickness, about double the thermal conductivity of aluminum.
Aluminum is acceptable, if the core thickness is increased and/or the the tubes are made larger. With cores, it's a compromise between thickness & airflow.
I have all my hot rod rads recored with domestic copper cores, and along with brass tanks, this combo is hard to beat.
The reason for aluminum radiators these days is cost, and not much more.
On the rare occasion I order a custom aluminum radiator, it's for fitment on a tubular frame or added capacity on a tow vehicle, and they always have the cores TIG'd to aluminum tanks, rather than attached to the lowest possible bidder OEM mass market style plastic tanks.
Originally Posted by FordCapriDriver
Aluminium makes far better radiators than copper or brass for sure.
My Escort has a aluminium cooling radiator and a copper / brass heater core, after much research i'm running VW G12++ Si-OAT ( Glysantin G40 )