Yes since mashed potatoes are not fried in grease like French Fries are that makes mashed potatoes much healthier to eat than french fries.
However if you bake the fries in an oven then the baked fries are healthier than deep fried french fries.
Mashed potatoes are also much healthier without seasoning or too much butter but it's okay to add seasoning and or butter to the mashed potatoes to make them taste much better.