Yes, there is no real value as the Micro-SIM will not be activated again once it is deactivated. Since the iPhone does not store contact information on the Mini SIM or the new Micro-SIM, you could give it to the buyer so that they may use it in the future if they need to a Hard reset. As the process just checks for a valid SIM from the Carrier. It does not have to be an active SIM.
You choice but again, the buyer can not reactivate the SIM, they will need a new Micro-SIM.
Dave