I think Joe gets Hagler coming forward. Marvin actually liked to box but Joe would box him and be countering him with sharp shots. I think he'd win the decision.
He was heavy-handed, but generally not a huge puncher, more of a wear-you-down type guy with his accuracy.
We're talking about power, not style. He was a boxer-puncher who could brawl, either way, he was a heavy-handed puncher, but generally not a huge one-punch type puncher.
How is Joe going to outbox Hagler? Hagler's more of a boxer than Calzaghe is. His boxing ability and technical skills were superior to Calzaghe.