Depends how it's made. Subs have the toppings laid flat, hoagies have then folded. Is it comparable to a generic sandwich? Then it's probably a sub. Is it more complex and richer? Then it's probably a hoagie. ------ Similar to soups vs stew, but the line is far more blurry. Hoagies and subs are not the exact same thing in my mind, although overlapping is a possibility.