The DLE redirects the definition of quizás to quizá, but I wonder if there's any implicit, secret rule that I am not aware of as to whether quizás is preferred over quizá.
I've seen both forms used almost indistinguishably even in the same text.
What's your take on this? Would you use both words in the same text? Do you have a rule to choose one or the other, depending on the word following it, for example?