I have a Kingston V200 256GB SSD. When connected to my SATA 6.0gbps port on my motherboard I'm seeing sequential read speeds of 300 megabytes / second.
When I put the drive into a sata to USB 3.0 enclosure and connect it to my USB 3.0 motherboard port my sequential read speed is maximum of 200 megabytes / second and average of 120 megabytes / second. I tried the enclosure on another machine and got 120 megabytes / second as well.
I'm guessing the enclosure itself is the bottleneck. Anyone know of reviews/benchmarks on enclosure chipsets themselves so I can buy something that isn't going to slow me down?