The current USB 2.0 specification runs at a theoretical maximum speed of 480Mbps
USB 3.0 promises a theoretical maximum rate of 5Gbps, meaning it’s 10 times faster than USB 2.0. USB 3.0 is also full duplex, meaning it can upload and download simultaneously (it’s bi-directional); USB 2.0 is only half duplex.
eSATA, an external connection that runs at the same speed as the internal SATA 1.0 bus, has a maximum theoretical of 3Gbps. This makes USB 3.0 faster than eSATA and about six times faster than FireWire 800 (full duplex at 800Mbps)
USB 3.0 also provides another advantage; while eSATA is faster than FireWire 800, unlike FireWire it cannot supply power. USB 3.0 has the advantage of being faster than both, even while supplying power.
Finally, USB 3.0 has improved power management, meaning that devices can move into idle, suspend, and sleep states. This potentially means more battery life out of laptops and other battery-based USB-supporting devices like cameras and mobile phones.