I'm curious to learn what nutritional benefits you see from chocolate milk, of any kind.
Here's a cup for cup comparison of coconut water vs. choc milk. Coconut water is much higher in electrolytes, and contains magnesium and potassium, which are vital electrolytes post workout. Milk doesn't contain them at all, but instead has way more fat and sugar. Not to mention, you're getting a low quality pasteurized / processed milk that in most cases is likely to contain hormones, antibiotics, preservatives, and chocolate containing high fructose corn syrup. Coconut water is a whole food. You can even find cold pasteurized and unpasteurized brands.