The Babel documentation lists both options but I did not find where it describes the difference. I found one Brazilian website saying "Use a opção brazil para escrever no nosso português" but it never mentioned the other option.
Reading the package documentation of babel-portuges:
Now we have to decide whether this language definition file was loaded for Portuguese or Brasilian use. This can be done by checking the contents of
\CurrentOption. When it doesn't contain either
I would say that
brazilian are equivalent.