The Glorious Democratic People's Republic of Korea
Democratic People's Republic of Korea is best Korea
South Korea has much better technology, as well as most of the developed world as it's ally in a war like this.
It would go something like this: North Korea's Zerg Rush ends on the bullets of South Korea's automatics. North Korea runs out of oil. North Korea attempts guerrilla warfare. South Korea commences Exterminatus. North Korea somehow sucks even more.
South Korea would easily get backing from the U.S. and western European nations. China may support North Korea but Russia would place sanctions on them and force them out of it.
backed by the U.S
A lot of it would come down to support. North Korea would at best get help from China. Whereas South Korea would likely have Japan, Australia, and USA to help fight.
The gap between the two has just gotten to wide for this to be a serious question.
At least South Korea has connections with powerful countries such as the United States, and North Korea is a national enemy to many countries so they would almost instantly help out South Korea.