During a recent weather balloon / high altitude balloon launch John Flaig, of Iowa USA, made this comparison between the Go Pro Hero 2 and the Go Pro Hero 3+ Black. Both recorded video in 1080 HD mode. The GPH 3 image ( on screen second) is clearly crisper than the GPH 2 (on screen first) and performs better in low light conditions.
For more information on the flight, go to http://www.nearspaceballooning.com/ .
The full video of the flight can be found at http://www.nearspaceballooning.com/launch-7/video/