So according to your explanation I was wrong. Even though in the situation I depicted the surface area is the same because both balls have the same radius the mass/drag ratio is different. The iron ball has a higher density and therefore a higher mass/ratio so it will reach the ground first...
Me and a few friends of mine were discussing if mass plays a role in the speed of a free falling body. They argued that equal bodies (same volume, same geometry) with different weights (mass) would fall at different velocities. I defended that mass has no part on the matter, but only air...