I was wondering if these two structure has similar meaning and use.
I don't wish to presume
means I don't want to be rude or have right to do that
with all due respect
is used when you are going to disagree, usually quite strongly, with somebody.
While the former stress on "not having right" and "not being rude", the latter is stress on " being disagree", the aim basically apparently the same : making suggestion.
I would like to ask which one more suitable when we make suggestions to someone who has higher rank in social ladder such as your boss or professor, especially in an email.