Objects falling from the specific height randomly.

Supposed i have a two ball on same position and falling from sky. when i play the game the object falling from sky for this i know we can use. “rigidbody.AddForce(Physics.gravity);”
but i want that object fall randomly means no one understand which ball fall first.I am using counter but its not work randomly.

var counter:int=0;

function Update () { counter+=1; }

function FixedUpdate(){
if(counter>200) {
rigidbody.AddForce(Physics.gravity); }

   	 	}

Use Random.Range Unity - Scripting API: Random.Range

Int aRandom = Random.Range( 0, 2);

var counter:int=0;

function Update () { 
   counter+=1;
}

function FixedUpdate(){
   if(counter>(Random.Range(190,210)){ 
      rigidbody.AddForce(Physics.gravity); 
   }
}

Something like this, perhaps?