Hearing aid technology can be complex. Each hearing aid has it's own on-board computer, constantly analysing your surroundings, and making changes to the acoustic response based on this information. Generally, the more sophisticated that computer is, the more automatically the hearing aid can adjust to your environment. Each hearing aid has a set of tools to try to fine tune that response. The greater the amount of tools and the more rigorously they can perform their duties, the better you will hear in a wider variety of complex acoustic situations.