Julian was more proven than John. John was knocked out by Duane Thomas with a thumb. I pick Julian by 3 or 4th round knockout in a very interesting fight. Round one would sure be tense.
It's hard to tell how good Mugabi was because I truly believe that Hagler fight took everything out of him. I'd give him a serious chance against any light-middle of the 1980s, and most middles too. McCallum's the one guy I'd outright expect to beat him at 154.
It doesnt matter who has more power. Which guy can box better and get that power to the target? I agree that is probabaly Jackson.
I am not sure Hagler too everything out of him. Marvin that night was rusty and didn't fight well and after Hearns I don't think he was motivated as much. His left was looping the whole night until late in the fight against Mugabi which proved how rusty he was. Mugabi gave him a good fight. I am sure the fight took something out of him,, but it was not everything.
They had different type of power. Julian had those quick sharp power punches. Mugabi swung and landed huge power punches like against Hargrove. No one could have taken that punch which knocked down Hargrove. Against Hagler either Mickey Duff planned for John to punch more conservatively or they saw during the fight that John couldn't throw those type of punches against Hagler, Mugabi threw shorter punches than in his other fights.