Anything painted black will conceal it better to the naked eye except of course, if you are talking auto body panel work using a gloss black. Flat or satin black tends to be more stealthy.
The look a sheen of aluminum draws the eye to it and basically opens up the flood gates of curiosity and questions.
Black draws heat to itself so theoretically it should keep the radiator a tiny cooler because it will extract the heat from within to the outside where the black is at. Old Nascar trick supposedly utilizing pigment thermo physics.