The question isn't whether it is tactically superior, its whether the shooting is cowardly. There's definite moral superiority in not shooting an unarmed man in the back versus shooting an unarmed man in the back.
I'm not claiming to have been behind a gun facing others with guns. Also, that's not at all relevant to this case, or any case of shooting an unarmed man in the back. I am, however, claiming that you have some sort of uniform bias and that's clouding your judgement.
I ask again, would it be cowardly for a suspect to shoot a police officer in the back during a chase? would the tactical superiority of the decision to do so impact your answer?