I recently bought an iOmega 1TB eHDD that supports USB 3.0 interface. Before I bought it, I wanted to know the fundamental difference in the xfer speeds of USB 2.x and USB 3.x interfaces. I researched a lot but could find only "official" notes on the topic.
I finally got my USB 3.0 interface compatible m/c and did extensive xfer checks over the last few weeks.
USB 2.0 m/c – USB 3.0 disk : xfer speed is 2.2MB/s – 3.0MB/s
USB 3.0 m/c – USB 3.0 disk : xfer speed is 50MB/s – 75MB/s
So, one gets an jump up of 25 times by using a USB 3.0 disk with USB 3.0 m/c for most cases.
Come back to learn more about performance on specific file types (media/doc/bin)