The density of a meteorite will affect the impact made on the Earth.
If we take two meteorites with the same mass and travelling with the same velocity, both of them have the same energy. The meteorite with the higher density will exert a greater pressure on the surface when it strikes the Earth. This follows from the fact that Pressure = Force/ Area. A higher pressure will allow the meteorite to go deeper in to the ground. It should be noted that though the crater here would be deeper its surface area would be less.
On the other hand the impact made by the less dense meteorite will be shallow but will cover a larger area. So you have a large crater that is not very deep.
To measure the density of the balls that you are using in your experiment, you can weigh them using the electronic balance. For measuring their volume, take water in a long cylindrical container in which the balls can fit. Fill water in the container and then submerge the ball completely in the water. See how much the level of the water rises. Mark the level after submerging them. Then take the ball out of the water and add water using a calibrated vessel. Measure the volume of water you have to add to bring the level to where you had marked it earlier. This is the volume of the ball. Density is mass divided by volume.