FWIW, I can tell you from perosnal experience, having a Firewire option too
is worth the extra $10-15 (USD), assuming you have the interface. Makes a
big difference in performance, perhaps as much as 50%. I'm assuming anyone
careful enough to solicit opinions prior to purchasing is probably more
sensitive to performance too. Trust me, firewire has it all over USB in
this regard.
Wasn't clear whether you wanted a pre-built unit, or just the enclosure and
would buy the HD separately. Rolling your own is trivial. Most pre-built
units only have a 1 yr warranty. Roll your own and you can save some money
AND grab a Seagate w/ 5 yr warranty instead. I have several enclosures,
some USB only, but the USB+Firewire unit I use most often I picked up from
Dealsonic.com:
http://www.dealsonic.com/arhdal3usb201.html
Argosy HD-360C (fanless design, so DEAD SILENT, if that matters to you),
that's a pretty good price for a USB+Firewire solution. When I bought mine
over a year ago, it went for close to $50, so it's dropped significantly
since then. Now add something like a Seagate 300GB, which has been on sale
at Fry's/Outpost for about $89 after rebate, and similar pricing w/ rebate
at CompUSA, BestBuy, etc., and you have a pretty good deal.
Jim