Transfer vs Reclass

I have a customer that has the following scenario. 

They have one operating unit with multiple companies. Company A and Company B (old companies) AP invoicing activity needs to be moved to Company C (new company) as of a particular date. What is the recommended approach:
1. Transfer all open invoices and purchase orders from Company A and Company B into Company C
2. Let the open invoices be closed in the old companies and perform a GL reclass of balance sheet accounts (AP Liability, Cash Clearing and Cash) at the end of the month. We can do this activity for 3 months during which all outstanding invoices will be either paid or canceled in the old companies.