I have both a Coolermaster ATCS 201c and a Lian Li PC-60...Of the two, the Lian Li is a tad quiter. It has less fans than the Coolermaster and it has the ability to change the speed of the front fans through the voltage switch.
On the flip side, I would still regard the Coolermaster as being a better case due to build quality.
To answer your question, a steel case with comprable cooling would be quieter than an aluminum case.