What your mates are talking about is the ability to select which drive is Master, IF it's on the same channel. The same channel means, connected to the same data cable.
Whether this is the case or not, remains to be seen and the easiest way to find out is to look inside the case. If you're quick and you have a conventional boot-up screen, you can sometimes see it there too, if you know what you're looking for.
On the back of each drive, is a series of little pins in sets of two. A jumper, is simply a tiny plastic block with a metal connector inside. By placing a jumper over one of these sets of pins, the jumper makes a connection, turns it on if you like - just like a switch.
Placed on the case of the drive,is a legend that tells you which of the pins to connect, in order to make a drive Master or Slave (there are other options too, but let's not confuse the issue).
Conventionally, the Master drive connects to the end of the data cable and the Slave drive to the centre connection. The other data cable end connector, plugs into the motherboard.
At the end of the day, I'm not sure it will make a whole lot of difference to your gaming experience.