Usually good to use a couple of characteristics on the computer. Serial niumbers are meant to be unique but I have seen casese where they are not. Also some tools are unbale to read serial numbers and default to a generic code which is duplicated across al similar devices MAC addresses are unique but devices generally have more than one - i.e if a PC is on a wired LAN is reports a different MAC address to when it is on wifi. Many tools use a combination of computer name and serial number. This is found to be sufficient in the majority of cases.