The Kids model is smaller and is designed for beginners. It only tilts from side to side, and has a lower height, making it easy to use. This model is the perfect addition to one of the other boards if your little one wants to join you in balance training. A tip for accommodating ultra-beginners is to place a book underneath each side of the board, which serves to restrict the lateral range of motion of the tilt. Doing this essentially adds 'training wheels' to the board, and gives you total control over how far the board can tilt. 
All of the boards have durable EVA foam which wraps around the ends onto the bottom. The reason i make them like this is to provide a good contact point with the floor so the board does not slide when one side touches the floor. This makes getting on and off easy and safe, and gives it a secure resting point if you lose your balance.