I would go to the AI suite
Only if you really like bloatware, or at least that is how I have found it any time I tested it. Asus may make good hardware, but they still have a long way to go with their software.
As mentioned by A Guy, there is no need for any software to control the fan speed as everything you need is in the bios. The big one is making sure that Cool and Quiet is enabled in the bios,
That should slow the fan down (and lower the CPU speed) when the computer is idle, as well as the computer will use less electricity. If it doesn't then try adjusting the Q-Fan settings,