It depends entirely on how you'd like your mashed potatoes to end up. White, red, or gold potatoes make a creamier dish, while baking potatoes produce a lighter, fluffier end product. For the fluffiest finish, spread your cubed, cooked, drained potatos on a cookie sheet and put them in a hot oven for 10-15 minutes. Excess liquid will evaporate, and your potatoes will fluff.