Milk is a lactose; disaccharide containing a molecule of galactose and a molecule of glucose. So, it is a moderately-glycemic carb which could potentially result in an insulin spike. That said, it is a simple carb. And the protein to carb ratio (if drinking milk for the protein content) is carb dominant.
There's no best protein per se. Find the one that fits intermittently with your macro-nutrient breakdown. So, depending on your diet and goals, check the supplement facts and figure if the amount of nutrients is right for you. For that reason, I prefer
ON Whey; relatively moderate nutrient to nutrient ratios.
Also, cosign everyone else.