Hearing aids are basically the same, in that they assist in recovering hearing. But they are not all made the same. That is, they do not all have the same level of medical technology, nor the same quality of parts and components. The state of the art today is digital hearing, with the capability of several levels of adjustment to custom fit your lifestyle and degree of loss.
Hearing aids have several styles of how they look and function - some are quite visible, such as behind-the-ear; others are all but invisible, placed deep into the ear canal.
Actually, the answer to that is simple: You have two ears. While that may seem a bit simplistic, it is true: your hearing is designed to gather sound from two primary directions. Our brains process sounds by comparing the input from two sources, which have different intensity and timing. To make sense of the multitude of sounds in a complicated environment, we need the capabilities nature intended for balanced hearing.
To determine whether a "binaural fitting" is right for you, you should consider these advantages: