From a health perspective, roast potatoes would be the better choice. There are few nutritional differences, but chips will have a higher fat content than roast potatoes, because they have a larger surface area and therefore will absorb more fat during cooking. The type of cooking oil used to cook the potatoes/chips will strongly affect the type of fats the food contains. For example, when roasting potatoes try using olive oil or sunflower oil, which primarily contain unsaturated fatty acids.