Cast iron is great if you want the material to hold a lot of heat... good for steaks, beans, stuff you're going to cook in the over over time. Copper and aluminum (hard anodized is better, I think, than cast aluminum) are better for things you want faster reaction to heat changes (sauces in particular). However, I like my copper stock pot a lot more than my coated cast iron one... looks cooler. :)
CBJ, some comps, a few awards, Certified Artisan Steak Taster.
XL Big Green Egg, Bubba Keg Convection Grill, Weber Kettle, Charbroil Infrared and mad livefire cooking skillz! :)