Defining Single Vs Multiple Inventory Organization for 2 Plants in the same Operating Unit.

What are the Pros and Cons. of defining multiple plants in an Enterprise as a Single I/O (with 2 separate Sub Inventories) as against defining them as two separate I/O's each in a Single Operating Unit. Both the plants in this case are adjacent to each other and both are distribution centers - one fulfilling for Domestic Customers and the other fulfilling for International Customers.

We want to understand the impact that the Single I/O vs Dual I/O approach is going to having from Planning, Forecasting, Order Entry & Processing, Inventory and Financial standpoint.

Any pointers towards this will be really helpful and appreciated.