Owing to different raw material have been used, the price of human hair is much higher than that of synthetic hair, so people may have different choices depending on their economic budget and needs.
Human hair can be styled, such as perm, dye or bleach it, whereas for synthetic hair, appliances shouldn’t be used including dryers or flat irons, it cannot be styled to look many different ways like its human hair counterparts.
Human hair looks and feels natural, you can treat it like your own hair, whereas synthetic hair has an unnatural feel, and its colour may be more shiny, the fibers may be very obviously artificial, as with doll hair.
Depending on what hair do your trying to achieve, both of them have advantages and limitations, you can choose to have both on hand as they each have their pros and cons.