[Solved] AddForce vs AddForceAtPosition?

Another stupid question, why

Code (csharp):

1. function FixedUpdate () {
2. rigidbody.AddForce (transform.TransformDirection (0, 0, 10));
3. }

and

Code (csharp):

1. function FixedUpdate () {
2. rigidbody.AddForceAtPosition (
3.     transform.TransformDirection (0, 0, 10),
4.     transform.TransformPoint (new Vector3 (0, 0, 0)));
5. }

produce different results?

edit: self-resolved... again