Either man could win, largely because the fight would be at 175. Mills could deal with a rough fighting type fighter that would come forward, especially a smaller one. Of course, LaMotta could fight light-heavies and he is clearly the more skilled fighter in this one. I reckon LaMotta could beat him, he's not going to get stopped, and the fighting ability of Mills isn't going to overwhelm him. LaMotta for me.
After Woodcock softened Freddie up in their rematch, Mills was a sitting duck. If Maxim could take him out, then LaMotta could have done it.