Consider the question ¿Cuál es el origen del modismo "es equis" para decir que algo no es malo ni bueno, sino "más o menos"? I tried to answer it, and long thereafter I realized, that, as is the case with many other questions of the type "where is valid this or that expression?", it's impossible to deliver a unique answer. One comes to that conclusion as follows.
Lot of people of lots of regions are allowed to say, "this is valid on my country or my region". Which answer should be there preferred over the others? No region can be preferred over other.
Even forgetting this issue, if we would be able to gather the information of lots of regions where that expression is usual, how would we know the information is complete?
Therefore, I ask here
Which is the wisest approach to those questions?