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Any SSD should be good in a USB3.0 enclosure (even older ones). I have a OCZ Octane 512gb SSD in USB3.0 and it tops out at around 180mbps while inside my old laptop it was hitting around 300ish. You're going to be held back by USB3.0 so there is no need to go overboard on the fastest SSD.
 
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If you are looking for speed, you will only be able to reach close to the max speeds of the SSD if its installed inside your computer. External drives are limited to the connection speed of the port.
 
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