Why Is better? StopCoroutine or Yield break?

I am developing a mobile RPG game... I need to know which is better for performance... I think are same, or not??

Code (CSharp):

1. private IEnumerator countdownAttack()
2. {
3.    yield return WaitForSeconds(1f);
4.    StopCoroutine (countdownAttack ());
5. }
6.  
7. or
8.  
9. {
10.     yield break;
11. }

 

You could probably build some benchmark test and run it many times and see how your test candidates perform?

 

Thanks... so, are the same? for stop any coroutine, as different methods for the same function?

 

The first one doesn't work, so I'd go with the second one! Also this is not a documentation question.