Well, yes, aluminum transfers heat more quickly than cast iron. The advantage of cast iron is not in how quickly it transfers heat; but in how slowly it transfers heat. The extra mass maintains it;s heat longer, so it will be more stable edge to edge, giving the appearance of being more even.For those that still believe that cast iron spreads heat better than aluminium, try the following:
Cut a sheet of parchment to fit the pan bottom. Place it in the pan with appropriate weights - say some dry beans. Put it over a gas burner until the parchment chars. Look at the char pattern.
Do this on both pans.
Adding cold food to cook cools the cast iron pan less than an aluminum one, making the food cook more evenly. This nis particularly important in quickly sauteing foods, esp. searing meat; as it browns it rather than steaming it in it's own juices.