I believe it is faster, here is why:
I have a Logitech Solar Keyboard. I had the unilink receiver plugged in to the 2.0 port and the keyboard would constantly lag to the point that I was going to return the solar keyboard to the store. I tried everything including contacting support, downloading the SetPoint app, switching ports (USB 2.0), etc... On a hunch I believed that the USB 2.0 port itself was the bottleneck. Sure enough, I plugged the unilink into the 3.0 port instead of the 2.0 port and never had a problem since.
I verified this later on because I have 2 additional monitors connected to my PC via a Diamond (BVU165) through a USB 2.0 powered hub. Whenever I would watch movies or youtube videos on the PC, after 2-3 mins, the hub would crash and I could hear my scanner (also connected to the hub) reboot and go through the warm up procedure (USB powered only). During this crash, the monitors would disconnect (turn black and go to sleep) and reconnect to the PC. I since attached a POWERED 3.0 hub which I connected the Diamond BVU165 (USB 2.0) through the USB 3.0 hub and never had a problem since.
I am not promoting this as a fix all for every device. Using the 3.0 ports instead of 2.0 seems to even out any sort of lag due to bottlenecks dealing with 2.0 technology and gives the devices the best chance of working properly.
Is there any studies to determine if USB 3.0 unpowered is faster than 2.0 powered?