Effect of density on speed of falling objects

[ajax0604]

If there were two objects that were of the same shape and size but different densities, how would this affect the speed at which they fall in air?
I've read that the mass per surface area unit is a factor but don't understand the science behind it.

 

[QuarkCharmer]

The drag force does take mass-density into account. If that is all that differs between your two falling objects, you could easily tell what effect mass-density has on the force.