From the standpoint of the North Korean people, even a Chinese takeover would be an improvement. As much as the South and many people in the North would like reunification, I don't see the Chinese as being willing to accept a border with a unified Korea run by the South as acceptable, and in many ways it would not be all that great an idea for a free and unified Korea to have a common border with China. Pretty sure whatever happens will be something that makes everyone unhappy.
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Correct on the part of China not wanting a N/S Korea reunification. China props up NK for one reason, and that is for a buffer from SK.
I was in SK the night President Park was assassinated in 1979, and we were all positive we were going to war with China the next day. Everyone knows NK cannot defeat SK on it's own, but if it does attack SK, China has no alternative other than to join NK in the attack.
Many do not know it, but the closest this world has come to global nuclear warfare was in 1979 when President Park was assassinated. At that time, the (then) Soviet Union (with their full nuclear arsenal) was fully behind NK as well.