Hi, I'm planning to buy WDC 320G, mybook premium (firewire, usb2) as a time machine backup disk (maybe to store superduper image file too) and also have 2nd FAT partition so my PC can use it also. Problem arisen when my friend finds out that WDC 500G, mybook essential (no firewire, just usb2) priced just a little bit higher compared to the above one. What should I choose? firewire or size? I'm confused. Thank's in advance!