I did some testing this morning, just to really find out what these three fan modes do. I changed to Quiet, booted and checked that it still was on quiet and started testing. I paid attention to fan sound, even measured it from the left side of the laptop with db meter. Also tried to listen how fast and how efficient they ramp up on different modes. The tests I made with 3D Mark Time Spy and with default settings.
First of all. Even on quiet mode if laptop works correctly, fans do ramp up. They do it little slower than on Performance and stay somewhat lower power too. Then again, the difference to the balanced mode is very small. On quiet mode laptop gave 45db, on balanced 50db and on performance 53db. On ears it sounded like the difference would have been much bigger on performance mode.
And now on the scores, Watts, Mhz and temps.
Quiet Mode:
Score 5675 (GPU 5985/ CPU 4388)
CPU MAX temp 88c°
CPU MAX power 44,9W
CPU MAX speed 4293Mhz
GPU MAX temp 60c°
Balanced Mode:
Score 6069 (GPU 5953/ CPU 6825)
CPU MAX temp 97c°
CPU MAX power 74,3W
CPU MAX speed 4293Mhz
GPU MAX temp 63c°
Performance Mode:
Score 6218 (GPU 6114/ CPU 6886)
CPU MAX temp 97c°
CPU MAX power 75,9W
CPU MAX speed 4293Mhz
GPU MAX temp 63c°
As you can see, the quiet mode actually affects very little on GPU performance, but much more on CPU. This can be seen also on temps, which are nearly 10c° lower on CPU but only 3c° on GPU. GPU stays very cool on every mode. It is also very easy to see which mode is the worst and it is the balanced one. On it the temps are as high as on performance mode, but the performance is little worse. So if you really need to get everything out of the machine, you need the performance mode (but then you really put heat on your CPU). On my games the quiet mode has been fast enough so far. Far Cry 3 demands most from CPU and has FPS round 60 on quiet mode, but it rises only about 10-15fps on performance so I rather use quiet. I dont see the difference with my eyes.
So here are my results. It would be great to see others too!
Quiet: https://www.3dmark.com/3dm/42755821?
Balanced: https://www.3dmark.com/3dm/42755979?
Performance: https://www.3dmark.com/3dm/42756130?