years ago my radiator guy told me that the reason my walker radiator ran hot was it was too thick. he recored my stock 47 ford radiator with a thin 3 row zcore. worked like a champ. he said that wrecker guys would come in and want bigger thicker radiators so they wouldn't overheat setting around. he would set them up with a 3 row and then not tell them. he loved it when they would bring in another one for that thicker core. the look on their face was priceless.
it's about air flow , not number of tubes. brass/copper goes out the window once you cover them in black paint. i prefer cross flow aluminum over anything else.