Multi Org difference between 11i and R12

The difference in multi-org in 11i and R12 is "MOAC" concept(Multi-Org Access 

Control)
 

In R12 we have a feature call MOAC(Multi-Org Access Control) which 
allows the user to submit requests, enter, view and access data of 
different Operating Unit without having to switch between 
responsibilities. 

Profile Options:

MO: Operating Unit - It will restrict the access through responsibility to only one Operating Unit

MO: Security Profile - It enables the user to get access on more than one Operating Unit by defining a security profile with Multiple Operating Unit and assigning it to the responsibility (If MO: Security Profile is set, then MO: Operating Unit is ignored by the system)

MO: Default Operating Unit - It is used when we have more than one OU attached to a responsibility through security profile, among whihc you want a particular OU to be defaulted during transaction entry stages. When the responsibility is assigned with only one OU then that will become the default OU, without setting the profile option MO: Default Operating Unit