When you or your landscapers are building retaining walls, you have the option of using natural stone or precast concrete. On its face, both are based on personal preference, but in many ways natural stone has the upper hand. It’s less expensive than precast concrete and more interesting to the eye (due to the natural differences between stones). It’s also easier to maintain and easier to replace should any damage occur.
It also looks far more natural when surrounded by plants and greenery. Precast certainly has a nice look, and it may compliment some decors, but for many landscapes natural stone will be preferable.