USB 3.0 is definitely faster at the as-designed level. USB 1.0 maxes out at 12 megabits per second (mbps). USB 2.0 is good for 480 mbps. And USB 3.0 can go as fast as 5,000 mbps. That means that you might expect a USB 3.0 external hard disk drive to transfer data 10 times faster than a USB 2.0 drive.
Since a typical USB 2.0 drive might transfer data at a real rate of 30 megabytes per second, can you expect 300 megabytes per second from USB 3.0? The short answer is no. The reason is not all because of USB 3.0, but because of the hard disk drive itself. Most traditional (with spinning disks) hard drives today top out with raw transfer rates at about 100 megabytes per second. That rate is limited by things like the rotational speed of the drive. You will never see an external hard disk drive do much better than that using rotating disks (although drives using Flash memory can be twice that fast), and it limits the ultimate speed of any external hard disk. In the real world, with data coming off of one hard drive and transferring to another through a modern operating system, you might see a real transfer rate of 50 to 75 megabytes per second using USB 3.0. This is 2 to 3 times faster than the same drive running on USB 2.0. It is definitely faster, but no 10 times faster.
Here is a typical real-world thumb drive using USB 3.0 reaching 67 megabytes per second:
With special hardware under ideal conditions, much higher speeds are possible (370 megabytes per second is demonstrated here):