The Gentle Typhoon is better IMO. They are both very quiet, quality fans. My observation is that the Noctua has some vibration problems. In free air, it's just as quiet if not quieter than the Gentle Typhoon... that is until you attach it to something. Then the vibration of the Noctua is transmitted to the case and causes some nasty resonant noise. Although Noctua includes soft mounting grommets, I don't think they will overcome its tendency to resonate.
The Gentle Typhoon also resonates, but it's easier to mitigate than the Noctua