Adding other business/organization entities or subsidaries

Good day,

Please help with the following scenario:

We have gone live beginning of the year on ECC 6.0 using only one company code. The other company entitites/businesses needs to be also implemented, so the challenge is to decide whether this will be additional company codes or another lower structure (Business Area or Profit Centre).

All other entities are in the same country as the company code that is already implemented, this means that legal requirements, currency, tax laws etc are exactly the same. The Chart of Account will be exactly the same, is it wise to create additional company codes for these or is it better just to use Business Area to represent these entities.

Regards and many thanks for all the help.

Kennedy.