The 5tier kit is ideal for everything the 3tier can grow and more.
The 3tier kit is ideal for a Herb Garden Planter for keeping a variety of 12 tasty herbs in one location and near by.  Water the top pot planter, and it self waters all the two tiers below until reaching the bottom saucer also included. The saucer used to catch in excess water especially for indoor gardeners.   
Simple: Just Plant & Stack
What To Grow: Herbs, Flowers, Succulents, strawberries, flowers etc.