More specifically, how did you come to the conclusion that functions are equal, from your premises that there are some things that one can do that the other cannot? Do you have real life evidence that prove the equality?
Besides, real life is inherently biased in that the environment in any given period may favor certain functions over others. For example, in this era of technology and advancements, the Intuitive functions are more valuable than Sensing functions, because Intuition drives more advancements than Sensing.
On the other hand, a few centuries ago the Sensing functions may have more value because tradition and stability are more valued and useful then.