Although Monzon may have been too big for Chavez head to head and fought in a more glamorous division, Chavez was the better fighter. Monzon had physical advantages over many of his most formidible opponents. That was rarely the case with JCC. Chavez beat them down with superior skill and superior will. I really can't think of any one attribute (skill, defense, power, chin, conditioning) that Monzon had over Chavez. Even if some of those margains are razor thin. Both men were All Time Greats.
Chavez didn't have height and reach, but he had plenty of advantages in power, durability, and stamina. I'd say he was quite gifted naturally.
Chavez is the better fighter...and in my opinion has the greater legacy. He fought better competition....he has more title defenses ...he was never an undisputed champ,but he was the man at 140 after he beat Taylor
Monzon never faced another all time great (Whitaker) He never moved up in weight . He retired while he was still on top. ( Delahoya , Tyzu)
I would give the edge to JCC. He was the best from 130 to 140. At one time Julio won 29 title fights I believe.
Monzon. Monzon, whilst ungainly, was one of the best ever at adapting to his opponent and punishing them. He had an extremely sharp mind, and comparable stamina. Chavez was pretty 'no frills' and one dimensional in comparison to Monzon. I would say Monzon does well against any ATG around his weight. Can't say the same for Chavez.