it all depends,,, hows that for an answer ?
the way ide / pata devices work is the master device dictates the speed of the bus
you always put a burner on an ide channel by itselft
I would have to say copying a cd from one cd burner to another AND both burners are on different channels, pri and sec ide, that would be faster
followed by copying a cd with one burner ( using the HD ) and the burner is on the sec ide channel either master or by itself.
followed by copying a cd with a burner and HD on the pri ide chan
there are other stuff to take into account like the hd buffer size, are the burners hd's pata or sata or a mix or scsi , system ram , how new is the hardware. All in all you may not even notice a difference in either. You should do a test. One of you go out of the room, then the othe configures the system as above , have the other come back in and copy a cd, have them write down what he thinks the config, do it again with another config see if he gets it right.