Customer Accounts vs Site Addresses

We have a couple of operating units; we are wondering what the “Best Practice” is for managing customers that are the same for both operating units.  

For Example, Customer ABC works for operating unit 1 and operating unit 2 billing is sent to the same place for both operating units.

What is the best method to set this customer up to accommodate billing and management of customer ABC, when there are two operating units.

Method A – complete separation, unique Party and Customer account and address sites for both operating units

Method B – Same Party used by both operating units but a unique customer account for each operating unit, the profiles at each address site would not be required as a unique customer account profile could be applied to all addresses sites within that customer account