You're talking about a good lightweight against one of the best at 135 ever. Arguello would make a tremendous account for himself because he always does...but I don't see Arguello winning this fight. Making it all 15 rounds? Sure. Hurting Duran? Sure. Winning? Nope. I think it's hard to envision him winning.
Duran is the ONLY former 135 pounder that I can think of who could either TKO or dropped BIG dudes like Davey Moore or Iran Barkley at 154 to 160 pounds....... "Moore & Barkley" may have lacked some fine skills, however, neither dude was ever called a weakling or *****....... MR.BILL P.S. Same for his 2 fights with Jorge Castro in 1997........... Duran was ancient and heavy at 165 pounds, but still strong and tough......... A normal lightweight CAN'T do them things, but Duran did..........
Arguello was a tremendous fighter. Great boxer/puncher. He had a good jab that he doubled up on a lot, great right hand, killer left hook to the body. The man was an offensive monster. Stamina, heart, and chin. The man just about had it all. Roberto Duran had a little bit more though. He was a better inside fighter, a more polished defensive fighter, had more speed, and better footwork. Duran UD 15. I doubt he stops a 135 pound Arguello who was younger and fresher than the version who fought Pryor.
Maybe against Hearns. Against Moore, Leonard (1st fight) Duran would roll with the punch and come back with his own right. Very hard to do. Duran mastered it.