Either one works for me, whichever is easier for Softrak, so long as the comment field is also available on the Contacts tab of the customer master record, so it can populate on an invoice (like the Contact name does).
If you are going to go to the trouble of adding a comment field on the Customer Contacts tab and Invoices Shipto tab, then why not go all the way and add optional fields? They should really be there anyway.
Thanks
Steve