It all comes down to what is important to you as the user. The S range of tablets (S2, S3 and the new S4) are the flagship models that contain all the bells and whistles such as super AMOLED display, more memory and processing power so that's what you're paying the extra for. The Tab A is more of a mid range option and contains most of the features of the flagships e.g. camera, WiFi or 4G (depending on the model) at a lower spec. To find out more please check out the Samsung Online Shop via the following link: https://www.samsung.com/uk/tablets/all-tablets/.