Three things, really: design, durability, and weight. You want it to be lightweight enough that it won’t tire your tiny traveler out while navigating exceptionally large airports, and you want it to be large enough that they will not outgrow it too quickly. You also want to make sure that it comes in a color and design that they can get excited about. Suitcases with their favorite cartoon characters are sure to get them excited to pack their bags weeks before you even leave. Many companies make additional covers at an affordable price if your little one happens to grow out of whatever character is on the exterior- saving you a little bit of money in the long run.