Bump because it got no replies. I’d slightly favour Hearns, Michalczewski is fairly unproven, never unified or fought out of Germany.
I can envision either of these scenarios depending on how well Dariusz is able to take Hearns' right.
Sounds like you never watched very many of Dariusz' fights. He was Victor Galindez tough. Very hard guy to hurt and a lot harder to discourage. It was the other guy's ability to absorb that is the problem in the matchup.
Rocky Rocchigiani (a solid-but-not spectacular puncher) had enough power to shake Dariusz several times in their 1st fight & essentially make him quit. Dariusz's chin was tested/proven against very few, if any truly exceptional punchers in his career. The closest thing to an exception may have been Richard Hall, & Dariusz employed a much more careful & methodical approach than usual in order to break him down.
Not sure about this one to be honest. While Hearns was an ATG, proved he could fight at light heavy and was a much better boxer, DM was durable, hit hard and was a natural at that weight. Had pretty good skills himself too. I suppose Hearns could theoretically win it but it might also be a dangerous fight for him