Its a significant change to deliver the speed increase:
1) Obviously the colour difference (should be red* as the 'red wunz go faster')
2) Power delivery - up to 900mA compared to 500mA (device build depending of course) to allow for faster / larger devices
3) USB 2 is unidirectional data flow (i.e. send or receive) where as USB 3 can do both at the same time
4) USB 3 has more wires (9 off the top of my head) compared to 4 for USB 2
The connectors are supposed to be more reliable BUT an user can still break them...
* USB 3.1 is spec'd as red but I think USB-C kind of got in the way
Need Pi spray - these things are breeding in my house...