Cotto is the better "single" body puncher. (Than Margarito) & possibly the best body puncher in boxing today when applied, IMO. Margarito's body work is more like beating the drum until it caves in.
Cotto will hit you on the liver and beat you. Margarito will re-arrange your organs. Both equally effective.
Cotto hits harder to the body while Margarito works the body more consistently. Basically, Cotto can stop you with one clean shot, but Margo gradually wears his opponents down on a regular basis with heavy body punching round after round. Thats the problem with Miguel Cotto's body punching... he's NEVER been a very consistent body puncher. If he were he'd be the best body puncher in the game hands down without question. As far as who's best between the two? Ehh, that's a matter of opinion I guess.
Overall body work, Margarito is one of the best in the world, takes solid shots to his head while throwing that left uppercut. Single power punch wise Cotto's left hook to the body > Margo's left uppercut to the body but overall Margarito's bodywork is better than Cotto's