First of what is JTAG?
A JTAG modification is done to the 360 motherboard, this modification allows you to play backup copies of games off a usb harddrive or even the 360's own harddrive. When you play games off of a harddrive to you no longer need the original game disc, instead you can keep them safe and unused for re-sale . This modification cannot be taken online with getting banned.
Now, let me hear it from you guys, what are the PROS and CONS of JTAG? What would you prefer?