Dark Chocolate is what you want if you are going to eat chocolate. Like Blueberries it has Antioxidants which work by neutralizing unstable free radicals- oxygen molecules that can be produces by environmental pollutants as well as the body's own metabolism.
most of your candy bars out there are milk chocolate or something else, though they to have antioxidants you would have to eat much more to get the benefits of Dark.
Dark is good for a treat but stick to the good foods if you looking to battle. Here is the top 20 list from CBS News
Small red beans
Wild blueberries
Red Kidney beans
Pinto beans
Cultivated Blueberries
Cranberries
Artichokes
Blackberries
Prunes
Raspberries
Strawberries
Red Delicious & Granny Smith apples
Pecans
Sweet cherries
Black plums
Russet potatoes
Black beans
Plums
Gala apples
Walnuts