They are different in any language and other than languages themselves they are rather arbitrary conventions. Use whatever typographic rules you like, as long as it communicates the ideas you like to tell...?!
How you communicate is sometimes more important than what you communicate. How you communicate can detract from what you communicate. How you communicate allows the reader better grasp what you communicate.
Following conventions & rules is exactly how you communicate those ideas. Failing to do so tends to cause confusion and distraction. It's not about what's right and what's wrong—it's about compassion for one's readers.
I would like to introduce the interrobang: ‽
?!: questionable or unsound move, but possibly strong
!?: seems to be a strong move, but possibly unsound
BTW, I thought these were all called interrobangs. Not so?