Mittens are generally warmer because fingers are not separated. Gloves, however, offer better dexterity and with modern insulations, they can nearly rival mittens for warmth. What do you choose? Think first about your child's outdoor activities. If they will be downhill skiing, where a lot of hand dexterity isn't needed, go for mittens. For all-around use, especially if your child will be dealing with boot buckles, heavy zippers, and snowball making, gloves are the way to go. Want a compromise? "Lobster" styles join your index and middle fingers together and your pinky and ring finger together to provide warmth and more dexterity.