Well, economically speaking, the DPRK would be way better off. IOTL, the North was more prosperous than the South until, what, the 1970s? The main issue, food, wouldn't be quite as significant since most of the food in Korea was historically produced in the South. A quicker resolution to the war would mean less damage overall to the Korean peninsula, so that's factor in. Also probably wouldn't see the North invest quite as much into military nonsense since they don't have the most militarized border in the world in ATL. Though it'd probably mean more spats with Japan over islands and territorial waters. Japan would probably have a standing military the way Abe wants them to if Korea was united under communism.
Other than that? Well, I wouldn't say it'd be more prosperous than South Korea OTL since Juche's autarkic outlook is a bit at odds with...well, just general economic growth in the modern world. I'm no economist but total self-sufficiency doesn't really cut it when your country is behind technologically and lacks basic resources like food and medicine. They still have TB outbreaks over there, apparently.
On one hand, I've heard someone say that Kim Il Sung and Park Chung He were cut from the same authoritarian cloth, just Park managed to wring out more money from his patrons that Kim did and their longterm economic visions were vastly different. But I don't think North Korea under the Kim family and its cult of personality would've been able to gain as much economic prosperity, not while they place their family's rule over the good of the people. You'd probably want to get someone else, a Deng Xiaoping figure or someone more open to the world, to lead them.
In any case, it'll mean Korea's further in China's influence than OTL after the fall of the USSR (I assume that Korea unifying doesn't change the underlying factors that broke the Soviet Union). Korea probably is forced to be on good relations with China. A tributary, so to speak. That's self-isolated in technology, economics, and diplomacy. That hates Japan after being occupied... Joseon Hermit Kingdom 2.0, basically, this time with a fancier name.