Cork vs Felt flooring underlayment-Acoustics Forum-Acoustic Fields Forum

Anyone have knowledge if 1/2 inch (12mm) cork or a quality felt underlayment is better for deadening sound transfer? This is for upstairs with plywood floors. I will not be able to do decoupling by building a drop down ceiling or anything. I was able to resilient channel, double 5/8 with green glue on the walls. But for the floors these seem to be my choices left.. Thanks in advance for your opinions !!!