A good screen recorder won't hit your framerate too hard. I've been using ScreenFlow (Mac only, $100) for all of my recordings and my framerate has little to no drops in any game (0-5 fps drop). Even when recording on the Mac side and going into my Windows 7 virtual machine I still get the framerate I would have without recording.
The difference between 30 & 60 fps is huge.
All YouTube videos I watch on my computer on my trusty old Firefox v28 run at 30fps.
Comparatively, if I watch the same video (of course, these would have to be uploaded at 60fps after YouTube started allowing this) on my iPad-Mini with the YouTube app, the framerate will be 60 (if applicable). The difference? The iPad video is much more fluid and smoother. It is much nicer to watch or play in 60fps than 30. 30 can be quite choppy compared to 60fps.
Cheers,
SM