Vector3D.distance

In AS3 I am trying to get the dstance between 2 3D objects by using distance method.

    if(Vector3D.distance(model.position,model2.position) < 100)

        {

            // do something

        }

..

>>You can use it directly as a method of the Vector3D class to get the Euclidean distance between two three-dimensional points.

Which point does this method pick? Is it the closest point to the other object ?

I am just thinking of how much time this would take in testing objects with large poly count.