This mode can hardly be recommended for any of the three system cases because each of them gets very noisy at the maximum speed of the fans.
Anyway, you may be curious to know the test results in the high-speed mode, too.
Antec Sonata IV (high)
Compared to the medium-speed mode, the Sonata IV lowers the temperature of most of the components by a couple of degrees more. This is comparable to the benefits from switching from the low-speed to medium-speed mode, except for the HDDs.
Antec P183 V3 (high)
The P183 V3 wins 2-3°C in terms of the HDD and chipset temperature after switching from the medium- to high-speed mode. The rest of the temperatures do not change.
Antec P193 V3 (high)
The largest system case in this review is almost indifferent to switching its fans to the high-speed mode. The temperatures only lower by 2°C. The graphics card even gets hotter when idle: there must be some conflict of air flows. So, this is far from the benefits we saw when we switched the controller from the low to medium-speed mode.
The next diagram compares the system cases at the high speed of the fans with the open testbed: