What is the difference between 〜となる and 〜になる?

Is it a nuance difference? Is it formality? EDIT For example: 請求書のお支払いは現金のみとなりますので、ご了承くださいませ。 請求書のお支払いは現金のみになりますので、ご了承くださいませ。 I just made that example up, but for some reason, my gut tells me it...