Put it simply compared to complex answers, with the same volume, but different densities, the question would only remain depending on the setting. If on a planet like earth with gravity, mass would be the main factor. So the more dense object would fall at a higher rate of speed. Acceleration would also be given to the heavier object, if they both begin in free fall. But if launched, the lighter object would have more acceleration for a short time if it is presumed the launch method is also presumed the same.
But for reasons of many things, the general rule of thumb to follow is terminal velocity. Check out some atmospheric pressures and densities, terminal velocity, kinetic/potential energy, newtons laws of physics, and basic speed research.