Riou

The GT's has a lot more static pressure than the Noctuas thanks to its large rotor. When the fan is on a heatsink/radiator, low static pressure fans will have less airflow than high static pressure fans. The GT or S-Flex would be better on a heatsink than the Noctuas.

For case fans, static pressure is not such a big issue except on highly restrictive grills/filters.

Chunky_Chimp

It's mostly due to the blades, actually. IMO, the P12 would be better if they hadn't cut those notches into the ends of the blades, that's just stupid, since it tarnishes how effective air can be focused. GTs, however, have blades designed with the complexity of the blades of an aircraft turboprop, designed to trap and shove air as efficiently as possible. One of my classmates has the AP-15 on his Megahalems, and I got the chance to examine the GT up close. It's really a nice fan, it would be nicer if the blades were full black instead of that whitish-silvery kinda color.

__________________

Sparky6string

If the GT is better on the Noctua NH-U12P than it is only marginally so and certainly not worth the extra noise to me. The fins on that Noctua cooler are spaced widely by design so that it works better with lower output fans. Considering I have two fans in push/pull I have more than enough cfm and static pressure.

The P12 does not have those notches, you're thinking of the NF-S12B. And since Noctua designs spring from the minds at the Austrian Institute of Heat Transmission and Fan Technology they probably have a reason for the notches, although they're beyond me also.