For charcoal use, the aluminum legs can melt if you place charcoal poorly. the cast iron has higher thermal mass but can't take the thermal shock aluminum can. Many camp cooks use the the aluminum for cheesecake and things they want to chill quickly after cooking.
Aluminum will have faster reactions to changes in heat. Cast iron will take longer to reach temperature but, will hold that temperature far longer and works better at high temperatures. Both cast iron and aluminum are reactive as well, so they are even on that score.
Its all about what the pots are used for and the context in which they are being used. Cast iron will do better with some foods and aluminum will do better with others. It all depends.
In general, I would tend to favor the cast iron over the aluminum for recipes that call for a Dutch oven. I am sure there are other pros that would prefer the aluminum for various reasons.
However, if you give some details about how you plan to use pot along with the foods going in it, we will be in a better position to give more detailed advice.