[ibmkg]

I cannot say much but what I will point out (again) is that for brass/copper rad you need better cooling. Say raising temperature beyond 100C (considering automobiles), one would end up discovering that Cu-Brass rad is just not good enough. These rads tend to absorb heat effectively but cannot get rid of it as effective enough (assuming using low CFM fan @ high temps). The result would be that rad would tend to get hotter and hotter.

Al on the other hand (even though may not absorb heat as effective as Cu-brass), the very property results it to be better performing at extreme temperatures @ low CFMs.
The reason being that they require less effective cooling methods (as there is not much heat to be removed due to the fact that they do not absorb much from fluid). Ultimately Al rad outperforms Cu-Brass rad and hence end up in automobiles.

If one can prove anyone wrong, they should experiment on varying temperatures with varying CFMs.