Migration best practice - Organization Structure, before or after?

Hello,

I am migrating from Goldmine 5.5 to MCRM 2011 and I have a simple question.

When you perform a migration, what is the better to do regarding the organization structure into MCRM:

- first migrate historical data's and pending activities (employees are still working with GM) and after setting up business units, teams and so on

or

- the scheme /setup of the organization structure should be performed before to avoid issues ? (if yes, which ones and what are the risks)

Thanks!