They have a lower glycemic index. But it depends on your reaction. The only way to know is to test after eating each along with the same amount of other food. I can say that for me the sweet potato fries are better. White potatoes always cause a steep rise in my blood glucose.
It does depend on how you react to them, and possibly what you eat with them - but I would not have either, just ask for salad or a low carb vege rather than putting so much high carb food into the equation.