First I need to confess that I find the 1960 original only fair. I like the bright color cinematography, but find the story rather silly.
The 1979 version of Jigoku features a better story at its center. An adulterous couple (a man and his pregnant sister-in-law) are fleeing the woman's husband (who is also the man's brother). They hide out, but are caught and the man murdered by his brother. The killer also mortally wounds his former wife and leaves her to die. However, the woman gives birth to a daughter before dying. This daughter, Aki, is fated to avenge her mother and end in hell. Twenty years later, Aki returns to her rural birthplace and begins to seduce her two half-brothers (they share the same father) leading to tragedy. In the last twenty or so minutes, the film switches to the underworld (hell) as we see the punishments the characters receive. I think life (and afterlife) is rather unfair to Aki since she is given no moral choice but is forced by fate to avenge her parents. Maybe that is just a westerner's opinion.
This version of Jigoku suffers from being way overlong, a half hour longer than the original 1960 film. Also, there are some noticeably ineffective uses of rear projection (the rescue on the train is one glaring example). As for the afterlife scenes, they are not as colorful as the original 1960 film nor do they improve in the FX department. However, the resolution is more satisfying than the ending of the original film.
Fans of the 1960 film might want to see this 1979 version for comparison sake. Also, lead actress Mieko Harada, in a dual role as both Aki and her mother, is quite good (Harada later had a good role in Kuroasawa's Ran). This version of Jigoku is not a bad film, but it is way overlong.