I think your TB enclosure is a tad slow... I'm using an Intel 730 SSD in an OWC Mercury On-The-Go Pro and get almost 500MB/sec read speeds compared to 400MB/sec in an OWC USB 3.0 enclosure.
My results seem to be quite comparable to other enclosures like the Seagate TB Adapter and, as mentioned, I have no speed complaints whatsoever.
I'm not surprised to hear that the Mercury performs well, although 500MB/s seems faster than any benchmarks I've seen. Barefeats did rank it as the best performing single-drive TB enclosure in a roundup they did back in August. Unfortunately, my Delock wasn't included in the testing though.
Another reason I'm glad I went with the Delock is that I prefer AC-power to a bus-powered solution like the Mercury. Also, I didn't have to pay for an included HDD I was just going to remove.
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