For testing I'll be using a Lenovo Thinkpad T500 laptop running Windows 7 Professional. The USB 3.0 ExpressCard was inserted and the driver software installed. The card uses the NEC USB 3.0 controller and comes with an AC adapter to provide additional voltage for USB devices. Without the power cord plugged in the drive would not spin up and was not accessible. However when plugged into one of the laptop's USB 2.0 ports or the USB 3.0 port on my desktop, the drive worked without any additional power required. The AC adapter is only necessary for the ExpressCard.
I tested the drive first plugged into one of the laptop's USB 2.0 ports, shown in the graphs on the left, and then in the USB 3.0 ExpressCard, shown on the right.
As expected, the ATTO Disk Benchmark shows that when connected via USB 2.0 the drive tops out around 35Mb/s throughput. However when plugged into the USB 3.0 ExpressCard we get up to 55Mb/s sequential speed, and better response on the smaller file sizes as well.
Similar results are seen using CrystalDiskMark, with USB 2.0 topping out around 34Mb/s and USB 3.0 again at 55Mb/s. Smaller, random read/writes are nearly equal, with USB 3.0 showing a slight advantage.
Finally HD Tune reveals USB 2.0 read speeds limited to just 31Mb/s, with USB 3.0 reaching up to 56Mb/s and averaging just over 41Mb/s. Access time is also slightly better with USB 3.0 and the burst rate is significantly higher.
Let's wrap things up with some final thoughts.