Adjusting sales-order/invoice unit sell price vs discount field

[Jeff Kowalczyk <..hidden..>]

Using branches/1.2 in a parts fulfillment workflow (SO->PO->Recieve->SI),
a user has traditionally adjusted prices of various line items for various
policy reasons.

These adjustments in their legacy system were done using line items
('courtesy', 'discount', 'write-off', etc.) with a negative amount. This
will not be the case with the LedgerSMB deployment.

What are the implications of allowing the user to a) vs. b): 

a) Set the line item part price to achive the desired result 

b) Calculate the discount percentage to achieve the desired result
(requires a calculator, inconvenient).

I'll train the users to do the recommended thing, but I would like to know
the implication of each approach on COGS, etc.

Thanks,
Jeff