here's the scientific facts on aluminum, cast iron, etc.
aluminum does in fact "hold heat" better than cast iron - that's the Specific Heat column.
aluminum will "hold" 0.24 BTU per pound of aluminum for each Fahrenheit degree it is heated.
cast iron is only half as good at "holding heat" -
cast iron will "hold" 0.12 BTU per pound of cast iron for each Fahrenheit degree it is heated.
so, an aluminum griddle/pan must weigh twice as much as a cast iron griddle/pan in order to "hold" the same amount of heat energy.