USB 2.0 tops out at 480Mbps, glacial compared to the 5 Gbps of USB 3.0. You'll never get exactly that 5Gbps throughput, since a) it's shared among the multiple ports connected to the same USB host controller, and b) many devices themselves aren't capable of reaching that level of throughput (spinning hard drives are a prime example).
Source: http://www.pcmag.com/article2/0,2817,2413310,00.asp
Questions
1) Does that statement mean that, when backing one USB 3.0 external HDD up to an identical twin, I should first dismount all other external HDDs for maximum throughput, even if the others are idle?
2) Will use of SmartSyncPro to perform the backup likely be faster than dragging folders from one drive to the other?
Thank you.