This is a great thread because all responses are excellent (until me :^P ).
I assume we’re talking about large read & write tasks, where differences would be significant.
If money is no object (just buy everything!...), then Thunderbolt with SSD is the way to go. I suppose that if storage and speed demands are huge, you could even daisy chain TB + SSD Raid enclosures. There’s probably little track record for that. At TB & SSD prices, it gets quickly to the price neighborhood of Mac Pros & high end solutions to slip drive into. (It’s possible someone might want (relative) portability with large storage and speed demands.)
Remember that TB solutions also include the cost of one or more cables at $50 a pop. USB cables are much less expensive.
With price in mind, getting an SSD with USB 3.0 will provide good speed with some future proofing and less noise compared with HDD solutions. If you plan to use with USB 3.0 to share data with many different (“foreign”)computers, there’s also less worry about widespread adoption of the TB standard.
http://barefeats.com/hard154.html
(Note the difference between the Koutech and the Voyager to see how the HDD limits USB 3.0 compared to SSD.)
With USB 3.0, there's also be the flexibility of using both SSD and HDD devices as needed at lower prices. USB 3.0 hubs are cheap compared to TB solutions. (You could also use a USB 3.0 dock with SSD and HDD & swap out as needed.)
With a bit more fuss and price ($200 to $300), there’s a third solution: eSATA. That might be a bit faster with SSD than USB 3.0. There are TB to eSATA devices from Lacie and Sonnet. It’s something to think about if you already have eSATA enclosures.
http://barefeats.com/hard153.html
you should go with a ssd. they really only have them available for usb 3.0 at a reasonable price. to get a 512 GB thunderbolt ssd cost like $800 so its probably best to wait on that one.
USB 3.0 and thunderbolt both max out hdds of that speed. The difference would be the same as any 7200rpm vs 5400rpm drive.
...7200 RPM car can achieve a top speed of around 110 km/h and the 5400 can achieve a top max speed of around 65 km/h.
The transfer mechanism is basically a road. The thunderbolt motorway can be traversed safely at around 900 km/h whereas the USB 3 motorway can be driven on safely at around 450 km/h....
Therefore it really does not matter because your cars cannot reach these max speeds anyway and the 7200 RPM car will be faster.
...there are other considerations, such as the latency of USB, but that does not matter when talking about performance of mechanical HDDs.
