Not splitting hairs, but they are both steel....its not cast iron v/s forged steel. One starts out as a forged billet the other is a poured casting.
Consider this, if you are a budget build (say <500hp) or a just for fun test and tuner, it probably doesn't matter much. If you are hitting it fairly hard, or drive the stripe with the throttle pedal, you should probably stay away from cast.
No they are not both steel
one is iron and the other is steel
its sort of like saying brass and bronze are the same
