Drag alone is enough to determine impact speed. Drag specifically counteracts the accelleration of gravity and in effect sets a limit on speed in a steady state environment. The atmosphere isn't really steady state as it gets more dense (more drag) closer to the surface.
Everything being equal though, aerodynamic drag is the limiting factor for an object falling freely, of which this event is a pretty good case of.
Weight as you note (more accurately density) does play a role as the more dense an object is the less surface area there likely is to create aerodynamic drag resulting in a higher velocity before drag = acceleration of gravity resulting in a higher terminal velocity.
But everything is not equal. It is true for a given object. A sheet of paper falling flat has more drag than if it falls on edge. But two same size balloons with the same drag and different weight (or density since their volumes are equal), such as one balloon filled with air and another filled with water, have different terminal velocity.
The first poster seemed to think that the heavier pieces were going to fall slower than the lighter ones. The chart I posted clearly refutes that.
Also, freely falling objects by definition do not have drag.