Now the question comes as to whether pure Brahman is upaadana or Ishwara or Jeeva?
Sankshepa Shaareeraka says that pure Brahman alone is upaadana as proclaimed in the scriptural statement "aatmanah aakaashah sambhootam" or from the Atman came space. Here Atman means pure Brahman as that is the strong meaning of the word.
Vivarana (Panchapaadika Vivarana of Prakaashatman) followers say that Ishwara who is possessed with sarvajnatva (all-knowing) and sarvavyaapitva (all-pervasiveness) alone is the upaadana of the world as put forth in the scriptural statement "yah sarvajna yah sarvavid, yasya jnaanamayam tapah tasmaat etat brahma naama roopam cha jaayathe" or "He who is all-knowing and whose tapas is knowledge, from him came apara Brahman and the world consisting of naama-roopa".
Also since in the sutras upaadana of the world is negated from jeeva, we cannot have pure Brahman as the upaadana as then jeeva would also become the upaadana of the world (since both jeeva and Ishwara have their substratum as pure Brahman). Sankshepa Shaareeraka negates Mayaavishista Ishwara (Ishwara qualified by Maya) as the upaadana and not nishkrista ishwara (pure Ishwara) as the upaadana of the world.
Maya Avidya Bhedha Vaadinah (those who consider Maya and Avidya as different) consider Ishwara as the upaadana because the entities from space etc. are transformations of Maya which is dependent on Ishwara. But antahkarana etc. are effects of avidya which is in jeeva and hence jeeva is also the upaadana. Thus both jeeva and Ishwara are the upaadana of the world.
Maya Avidya Abhedha Vaadinah (those who consider Maya and Avidya as same) consider Brahman alone as the upaadana of the waking world whereas jeeva is the upaadana of the svapna prapancha alone. Antahkarana etc. are identified with jeeva and this identification makes jeeva seem as upaadana.
Few others say that jeeva alone is the upaadana of the world like svapna prapancha (dream world).
Once we understand the illusory nature of the world, then we can choose any view that makes us apprehend the world clearly. Personal view would be to consider Brahman as the abhinna nimitta upaadana kaarana of the world. Brahman is proclaimed in janmaadi sutra as the material cause of the world. Brahman also has to be the nimitta kaarana as Brahman alone is sentient. This Brahman is not pure Brahman as pure Brahman cannot transform or become an efficient cause. Thus Brahman associated with the power of Maya is to be taken here. The efficient cause is Ishwara who is Brahman associated with Maya. Ishwara cannot be material cause as a sentient entity cannot transform itself - hence it is Maya or the power associated with Brahman which is the material cause getting transformed into the world. Since both Ishwara and Maya have their substratum as Brahman, therefore Brahman is the undivided material and efficient cause of the illusory world. More analysis can be had from the "Satya Darshanam" work found in Articles or here.