Let me brief you about both MRC and Multi Org. MRC stands for Multi reporting currency . which means you should have different SOBs, One must be primary and others are reporting. (max. 8).

Where as Multi Org concept is we will set up a organisation where we will have a Business group then SOBS then Legal entities then Operating units then Inventory organisations and lastly sub Inventory catagerory.. This set up will help to avoid multiple installations and have only one installation. We will attach all sub ledgers like AP, AR etc at Operating level and GL and FA at SOB level..

HR at Business group level.. There is a lot to discuss on this topic. please refer any avilable oracle material for more details.