Don't get rid of your Hero2 just yet! Interesting comparison

[Interceptor121]

So faster shutter speed gives less image blur in each frame so when software selects every other frame to render, it is taking a sharper image to process. When you have an absolutely stable camera, it is less noticible but the compounding of camera and subject movement is very noticible.

It would be good to know if YT/Vimeo are frame dropping or frame blending to get from 60fps to 30fps. One will be "sharper," the other will possibly be "smoother."

I can post some 960 48 fps video and it is very clear that as my mask mounted GoPro2 moves, there is image blur that seems to "snap" into sharpness as my head stops moving and I fix my gaze on the target. I don't realize the "snap" into sharpness at lower frame rates.

Don't forget that there is not just shutter speed that comes into play with the framerate calculation. Without extremely well-lit conditions, faster framerates have lower maximum shutter speeds, but they also push gain to maintain exposure, so there's a multi-factor back and forth that affects brightness, sharpness, and noise all at once.

No frame blending not dropping h264 is temporally compressed you need to decode it and then re-encode so it is a whole new file unless you are within the specifications in that case it takes it nearly as is
And gombessa is right if the exposure value is fixed as the gopro has fixed aperture increasing shutter speed requires increasing gain which mean increasing noise
When there is plenty of light no problem other wise the footage gets grainy
You need to work out yourself what works for you taking into account that is you use a filter you already effectively doubling the gain to recover the loss of light the filter generates