I've used both a number of times, and for default settings, both are pretty easy to use, though different. However, where Nvidia is much better, is the custom profiles for individual games. With AMD, you have to create a profile and save it. To use that profile you either have to create a shortcut and launch the game from that shortcut, or you have to launch it from a CCC menu. This is annoying imo, but other than that, they are both pretty easy to use.
Note: It has been nearly a year since I've used the CCC, so I suppose it could have changed.