Pre-Sales Support - use Oracle Task or Oracle Service Request?

We sell components that a customer can assemble various ways into a final system (think Home Depot for scientists and engineers).  Our sales force often needs from our technical support team to close opportunities.  For example, if the field sales engineer has told a customer that a certain system can be built with our products, the customer may want proof.  So the field sales engineer will request help from our technical support team to complete the proof of concept.  The help we provide needs to be tracked and needs to be associated to the opportunity.
The tech support organization also provides post-sales support to our customers and they track this using Oracle Service Requests.  I need to recommend whether to use the Task or the Service Request.  Either way could work but I am interested to know if anyone else has dealt with this issue and what they learned.