MRC Responsibilities upgraded from 11i to R12

Hi

We are upgrading from 11.5.10 to R12.1.3 and I would like to know if I need to create R12 MRC (Reporting Currency) responsibilities when I create a new ledger with a reporting currency ledgerin R12.   It appears that I can post, view, create journals that pertain to the MRC ledger directly from the primary ledger .   What should I do with the upgraded 11i MRC responsibilities.  What is the benefit of keeping the 11i MRC responsibilities if everything can be done from the Primary ledger?

Thanks Laura