Too close to call. But Hagler went up against Hart, Mugabi, and Hearns...so in terms of a proven chin, I would say Hagler by a slim margin.
I've read articles on both fighters which mentioned they had thicker skulls than would be considered normal.
Very true, like I was saying Chavez fought for A guarter century, he had a lot more wear and tear than Marvin had. Both guys had skulls of iron, to close to call..
Hagler, quite comfortably. He fought the toughest MW's of his time and whipped them all. I can't quite say the same thing for Chavez in his respective divisions.
Divisions is the key word though. Hagler stayed in one division where Chavez moved up the ladder where his opponents hit harder and harder.
I want to favor Hagler... He fought EVERYONE on the rise in his career and during his title reign. Never dropped (please no Roldan cuff reference) and really never got buckled. Hart,Briscoe,Hearns, Mugabi,to name a few. He engaged everyone toe to toe, and wore them down with his toughness as well. I followed Hagler`s career from the start and was always incredibly impressed by how rock-solid that chin was. But, Chavez was right there too ! Moving through the divisions, he always took everyone`s bombs before grinding all his opponents down. The knockdown by Randall was a past his prime Chavez, so I even give him that one... All in all, I think you have to call it even ...
Perhaps Hagler by the slimmest of margins. I never saw him really hurt...Hearns buzzed him briefly sure, but who else? Chavez had an incredible chin too though, make no mistake. How he could walk through Rosario's power shots without changing expression baffled me, and to be fair he did climb several divisions whereas Hagler did not. However, he was wobbled a bit by a Camacho uppercut during their fight and Mayweather seemed to stun him a bit at one point during their second fight...so slight edge to Marvin for me.
Chavez hardly moved up that much in weight.He was a huge 130 fighter that struggled at the weight there by the time he reached world level and ended his relevant career at 140. Basically a lightweight sized fighter that moved up one junior class.
Yeah, Rosario was regarded as being one of the most feared punchers at the time having blasted out the previously iron chinned Livingstone Bramble and was actually favoured by many to not only beat Chavez, who was moving up from 130, but to knocked him out. It was arguably Chavez's finest performance.
Hearns did not hit Hagler with his best shot, because Hagler was smart to switch styles and become a whirlwind and not give Hearns space. Hearns's right hand was most powerful when he got distance on it. Cuevas, Duran, Shuler...all of them came when he got distance and extension on it. The shot that buzzed Hagler a bit was a short right hand. Hearns landed some looping right hands at distance, but nothing like his vaunted right hand with full leverage and extension like he did on Cuevas, Duran, and Shuler. That's not to say Hagler wouldn't have been able to take it. I thought Hagler walked through bigger shots against Mugabi, that landed more flush. The most I've seen Hagler hurt was at the end of one round in a fight, I think against Hart. My pick would be Hagler, just basing on the fact that we did see Chavez get briefly rocked against a modest hitter in Taylor, when Chavez was in/very close to his prime, also rocked in the 8th against Whitaker, and dropped and hurt against Randall. We never saw anything like that from Hagler, getting dropped and hurt like that.
Chavez was hurt later in his career but Meldrick Taylor never hurt him. He walked through everything Taylor threw without any effect.