What is one advantage of prezygotic isolation over postzygotic isolation?

With prezygotic isolation no energy is lost trying to produce a zygote that is not viable. With postzygotic isolation a viable zygote may be formed and born but it will be sterile and so a lot of energy is expended to nourish and raise an offspring that will not be able to continue the genetic line. Prezygotic isolation is more energy efficient in a sense.