Although it sounds like a money-saving proposition, choosing all-in-one shampoos and conditioners is really just a gimmick.
Shampoo does one thing and Conditioner does something else. Using them together, you get the benefits of neither.
Either the shampoo cannot get inside to cleanse due to the properties of the conditioner, or the conditioner gets diluted by the shampoo and fails to work properly.
Choosing the right hair care products is a personal decision which should be based on what your hair needs and what you want your hair to look like. Your hair care professional can best help you choose hair care products by evaluating your hair's needs, your desired end result, and your budget.