They're literally nothing alike aside from being considered too old to be competitive in their chosen sport.
Also, Mares is an exceptional talent whereas Pavlik was just a normal one.
I don't recall Kelly Pavlik getting knocked out cold. Also Pavlik had an alcohol problem before that fight, although I am sure the loss didn't help that issue.
I have never heard of Mares having any issue like that, either before or after the Gonzalez fight.