I am about to purchase the 250gig external HD from Lacie, and they come in 2 flavors, usb 2.0 & usb 2.0 FW800 FW400; since i only have a macbook i wont be using FW800 too much, but i have been hearing that its due for a speed increase.. is this software-side only? because then i would definatley like to future proof my HD; otherwise USB 2.0 is cheaper and faster (i beleive) than FW400... thanx