I think betting on Mario Barrios is more reliable.
Watching some of Manny's training videos actually convinced me that he won’t go down that easily. He's old, but he's clearly on a mission to prove that age is just a number. In fact, he even gave a guarantee to fans who are worried about his comeback, saying that he knows his own body and understands exactly what he's doing.
So , just for fun, I think I’ll take a shot and bet on Pacman to win ..either by decision or KO.
Two different outcomes, two bets. Why not?

Pacman is the only champion in 8 weight classes and definitely one of the best boxers of today, so even at 46 he can knock out many more boxers and his training is impressive.
Nevertheless Freddie Roach was against such a Pacman comeback and considering their long-standing partnership you can definitely say that he is worried about Pacman. In addition, his opponent is not just average boxer, but still a champion in this weight class and it will be more difficult to knock out such a boxer than a passable opponent.
In general, my heart would like to bet on Pacquiao, especially on a beautiful knockout, but my mind says to bet on Mario Barrios.