I am looking at buying an external drive for use for time machine backups. From what I understand firewire is faster than usb, but how much faster is it really in real world use? Is it worth the extra cost? I can get a 1TB usb drive for about half of the cost of a firewire unit as it seems the usb are always on sale. I can envision the initial time machine backup taking hours and hours but after that it should not be a ton of data so the speed difference shouldn't be that noticible or will it? Right now I have about 400 GB full on my hd and I rarely have more than 2-3 GB of changes in files on any given day.