By the way, a younger Mosley would beat Pacquiao and Mayweather in my opinion. So I am in fact very high on that version of Mosley. But Manny fought Mosley literally a decade after his prime!
Ali is a tough case to judge fairly. He looked untouchable pre-incarceration, but the competition, aside a bit faded Liston, was subpar. His post-incarceration competition was the best of all-time, but he had many bad moments and perhaps should've given more decision losses, but then his reflexes had clearly eroded. And like Roy Jones, he depended so much on his reflexes.
The best versions of Duran stops the best versions of Pac anywhere between lightweight and super welter. Duran was simply a better all a round fighter. Pac best fighting was done at featherweight super featherweight, it's where he beat his best competition. Above that is quite a bit of past prime opponents looking for big payday. Hoya, Cotto, Mosley, Thurman, etc. All were at the tail end of their careers. Giving Pac a lot of credit for those wins is similar to giving Norris a lot of credit for beating Leonard. Or Spinks alot of credit for beating Holmes. Etc..
Duran. He was just that bit better. Both men though were two of the greatest pound for pounders ever.
Pacquiao was one kind of a fighter,but if Horn managed to dirt his way into pac with a slopfest inside the clinch,not sure how he'll receive Duran's mauling skills.
This is a pretty silly way to analyse the match-up. The open-stance orthodox-southpaw matchup is far, far more complicated than just getting your lead foot on the outside and spamming straight rights. Southpaws are hugely aware that this is what orthodox fighters want to try do to them, so have devised a number of ways to stop this from happening and to counter this position. Manny was very good at these sorts of southpaw shenanigans.
Maybe Duran beats him. I just reject the suggestion he was leaps and bounds a better boxer. Manny is a pound for pound great.