Here is a video from the Panasonic V720. Its not the best clip just one I could find and upload quickly. This video on YouTube seems to be less grainy but it does show how the motion really blurs the image. This was shot on auto so the shutter speed is really slow. at the end you can see some of the noise in the sky.
TBH, that's pretty good for a camcorder. Except for when you're zooming in, I don't really see any major noise in the image.
Regarding the HF M50 in low light, you can raise the video gain and remove the video noise (small specks on screen) in post with denoising software.
Perhaps you can raise the gain on the Panasonic as well?
Camcorders have a small image sensor. Is there something specific you need night video shooting for? If it's really imperative, consider a larger sensor DSLR or mirrorless camera.