I actually don't think tito had that bad a chin, more of a balance problem, however in this fight i would say he gets knocked out, hearns has got the reach advantage, more speed and power and is the much better boxer, if he keeps this at distance he will KO tito If tito can bridge the distance a bit and take some of hearns bombs while doing it he could score the upset as he has the power to take tommy out, however he shouldn't be favoured to win IMO
Hearns, because he started faster and flowed with his punches. Trinidad was always vulnerable to jabs and the Hearns' right hand behind it spells trouble. I think Trinidad's best chance is to catch Hearns during a mid-distance exchange, drop him, and stay on top. But regards to generally controlling the action for as long as it lasts, Trinidad doesn't have the jab and fluid combinations to be bossing the action. He's got no option but to come forward as when he's back pedalling he's either covering up from his opponent or setting up his next attack. He needs to get set to get off and when matched against Hearns style and speed he's getting caught. Hearns can hit on the move with the jab 'freely' and scores better in all directions. Hearns gets to first Trinidad based on styles. KO3.
Hearns's chin gets univerally underrated IMO as well. Both are capable of starching the other with one well placed shot though, so it doesn't really matter. What does matter is Hearn's advantage in pretty much every other area. Hearns by KO before the 5th.