The main thing which makes dark chocolate so healthy is the increased cacao concentration. This is why the more bitter the dark chocolate is, the healthier it's going to be. The average person eats dark chocolate at a concentration of about 45% cacao, which honestly isn't all that much. To get the real benefits, anywhere between 70-90% cacao is recommended.
I personally skip the middle man and just take pure cacao, in the form of a hot cacao drink. I mix pure cacao with a bit of coconut oil, peanut butter and honey, and stir it all together with some water. Milk enhances the flavor (as it does with most hot chocolate drinks) but I choose to use water due to a minor lactose intolerance.
Dark chocolate is my favorite kind among other kinds of it. I also choose dark chocolate whenever I am baking or making that chocolate ganache for a cake or muffin. Some people don't really appreciate the bitter taste of dark chocolates as they don't really like the high cocoa content in it that makes it bitter as well. I like it because it has low sugar content and great for desserts. I am really not a fan of sugary sweet desserts.