Knowing what you will be using the office chair for and how you will be using it are probably the two most important factors that should influence your buying decision.
If you are an executive who spends part of the day in front of your computer, but also long hours in meetings with colleagues and visitors, you definitely need a fully adjustable chair so you can sit back and look relaxed and friendly when you have someone on the opposite side of the desk, yet get all the necessary neck, shoulder and back support when working on your computer.
Someone who uses his or her office chair exclusively for computer work should place a heavier emphasis on ergonomics (see below).