[strken]

I prefer medium roasts over light roasts, which isn't quite the same thing as dark roasts, but it's because it tends to get rid of fruity and acidic flavours and lets the richer flavours come to the front: brown sugar, chocolate, malt, nuts, spices, etc. which I prefer in milk drinks.

No idea what the dark roast people are after, but maybe it's the same sort of thing.