Which call is more expensive?

Questions & Answers
1

Is there a difference in these two calls?

this.gameObject.transform.position = Vector3.zero;
transform.position = Vector3.zero;
2

Yes: gameObject is a property, thus the first line includes a call to its getter function. The second line calls directly the transform getter function, saving one call. The this keyword makes no difference, because the compiler attaches it automatically. The two lines compile to something like this:

this.get_gameObject().get_transform().set_position(Vector3.zero);

this.get_transform().set_position(Vector3.zero);