You approach this question from the wrong point-of-view. From the Iraqi point of view it would be "why have I lost so many of my countrymen, tanks, air defense, and artillery to the Apache in comparison to the Cobra? The answer to your question will be self-evident.
Marine or Army aviator, Cobra or Apache, all will bring the fight to the enemy with equal zeal and intensity.
As for the last, third hand information (unconfirmed)...they were called in after a mission, responding to a convoy that had been ambushed and about to be overrun. They provided close cover until wounded could be evacuated before they were shot down. They stayed to fight. Both are said to be recommended for the DFC.