Benefits of ST/OT - 1 implementation for 4 countries

Hi,

I'm working on JDE implementation for a client who has 4 companies in different countries (2 of them with manufacturing). Historically they had 4 different systems and users are keep asking if it's possible to create a sales order in the manufacturing company based on purchase order from the other companies. The reason for this is that the non-manufacturing companies treat those that manufacture as one of their supplier, and they want to keep control over their purchase orders.

What benefits would the Transfer Orders ST/OT approach have over standard purchase orders with the incoming EDI for "related" sales orders?

Thanks for your thoughts and comments.