Unity indicates the infinite,duality the finite.The infinite is eternal,the finite,temporal.
One of the difficulties with the 'Oneness' concept is the easy excuse it becomes for not worshipping..or 'doing' anything about one's belief in a Supreme Being ..(perhaps it is the very word
being that gives the clue to the answer here) ..the argument is the rather shaytanic one of,"If I
am God already then why do I need to worship Him?"
Here is something on the subject...
Misunderstandings regarding the status of the World-process.
There has been a lot of misunderstanding regarding the status the phenomenal world in Advaita, even by some of it's modern proponents. According to this false interpretation in which the universe is considered nothing but illusion. Many people therefore reject Advaita as "illusionism". But in fact Shankara was a staunch empiricist and fully acknowledged the phenomenal reality of the world,
God (Ishwara) etc. He was actually very critical of the
Yogachara Buddhist position that the world is a subjective product of the mind). When Shankara discusses the reality or otherwise of the world of duality, he is talking from the point of view of his attainment of Enlightenment, according to which the world-process really did appear unreal or false. But as far as the ordinary consciousness goes, Advaita propounds pragmatic realism,
including worship of deities separate from oneself, etc.
What Sheikh Nazim always says about this is,"The Lord is always the Lord and the servant is always the servant."
By rhyming language we know that "The rope is always the rope and the serpent is always the serpent." !
My way of resolving it is to say that what Islam says rings true..even though nothing exists except Him..He created us in this illusory form in order to test us and..see if we can remember where we came from and worship Him ..etc etc blah blah blah ..