Socialism

Chernobyl could be argued to be worse, at least from a theory perspective, because in an idealized Soviet/Communist system where the working classes are actually looking out for worker interests, the plant operators would have known about RBMK reactor flaws (and probably also would have built a containment building like Western reactors have) which likely would have prevented the disaster. At some point there was some breakdown for whatever reason that prevented this. On the other hand, at Bhopal, there was essentially no hope of worker control at all because it's built within a capitalist system. Profit at the expense of lives is the expected outcome in this system.

tl;dr, it would be nice to see Communists et. al. hold their societies to a higher standard than simply not being as statistically bad as capitalism