USB 2.0 is limited to around ~500ma while 3.0 can supply more, so a USB 3.0 port should be able to charge similarly to an outlet wall charger.
As far as I know the cables themselves are similar, it's just the ports and devices that are different. That doesn't mean a low quality cable won't limit performance though.
Edit: It's also worth pointing out that some OEMs (Apple, HP) use non-standard USB cables as a way to force people into buying replacement parts from them. These cables are, by definition, not quality and can cause all sorts of weirdness when used with anything not made by that company(eg. ipad + apple cable + non-mac usb port). Basically, if the device can tell the difference between a generic good quality usb cable and the one it came with then it uses a non-standard cable.
This is especially important since USB 2.0 ports can't handle the same amount of load a USB 3.0 can, so if you have a cable that's been modified and a device accidently draws more power than the port can handle you're going to be left with a burned out/dead USB port.