Neither is worthy of being called "chocolate". You can barely get a hint of cocoa in the taste, the overwhelming taste is just sugar with a cloying stickiness of palm oil.
Galaxy ingredients in descending order of percentage contents: Sugar, Skimmed MILK Powder, Cocoa Butter, Cocoa Mass, milk fat, Whey Permeate, Palm Fat, Emulsifier (Lecithin)
Dairy Milk ingredients in descending order of percentage contents: sugar, milk solids, cocoa butter, cocoa mass, vegetable fats (palm, shea), emulsifiers (E442, E476), flavourings.
Actual decent quality chocolate ingredients in descending order of percentage contents: Cocoa Mass, Sugar, Cocoa Butter, Vanilla