Because for 475 visa, u have to reside for 2 years within 3 years after grant. If grant is made now, I have to go settling there by June next year. But now, I am not ready to go there.
in that case,try to find out some reason to case officer,for example,u have no way of giving up present job contract temporarily,your wife is pregnant and so on,anyway,i do not really consider deferring is a good idea.so i do not have any preferable opinions.