The theoretical transfer speed of USB 3.0 is 4.8 Gbit/s (600MBps) vs. 480 Mbit/s (60MBps) which is a 10X improvement. Sustained transfer speeds (real life) for external hard drives are about 85MBps for USB 3.0 and about 22MBps for USB 2.0, so about a 5X improvement but still a significant advancement in transfer speed.