I think the decideing factor is 135 was Duran's best weight while Chavez was better at 130. I think Duran would win.
I think Chavez was better against Rosario at 135 than he ever was at 130. More experienced, showed how he would fair against a true elite for the first time, and was more impressive doing it than I've ever seen him otherwise. Either way, Duran was just a bit better.