The thing is, that if you consider only 120 and 140mm fans, there is not much difference when it comes to reduction of how many fans is used.
But if we try a 180mm fans or larger, it really starts to kick in. Even slowest GT's will be aduiable if you have really many of them, and that is exactly what happens in high end setups. Imo the way to go is to get a big square rad 360x360 and put 4x180 on it. Only four fans total, even if it is worse than 9x120 in terms of performance, it is just lot quieter. And I am not talking here about how many fans doubles the precieved loudness. It doesn't have to double to be worth reducing. People want to do really crazy stuff to increase performance of their setups by few % (going for shrounds, picking very specific hard to get fans). There is also plenty of people who would want to use every opportunity to make their setup quieter. And if we have such large rad it will also perform very well, just because it is such overkill, doesn't need to be optimal to be enough for great peformance results. I think there is more people who went for overkill rad setup disappointed because their system is loud, than people who actually complain about performance.
