I have a LaCie 3 interface drive...has FW 400, FW 800 and USB 2.0, its really a good drive. I'd recomend it...I also have a Maxtor USB 2.0 and 1.1...I had erase it when I first got it(even thought there wasn't anything on it) to allow me to put things on it, but it was on sale, so I don't care. Works fine, but I like the LaCie drive more, if you can get FW 400 and USB 2.0(FW 800 is nice, but few computer have it)
FW 400 is nice for your computer( a Mac) but if you need to using on a PC, not all have FW 400, so USB 2.0 is nice to make sure it works with most computers.