Opinion Piece:
Floyd fought fighters in or below his weight while Manny fought a light heavyweight in his first exhibition bout.
Floyd fought fighters he could easily beat while Manny took a gamble with a big fighter, who packs a solid punch. Pacquiao's toughest fight was with Margarito not because of his skill but because of his size, durability, and weight which carried more power in his punches. Mayweather's exhibition opponents are not known to be heavy hitters with the lone exception of Jake Paul.
Interesting side note, Casimero had his bout stopped due to an "accidental" hit at the back of the head while Pacquiao nearly had his bout stopped for the same incident. The difference is Manny took it up a notch and floored Yoo twice en route to a UD win. John Riel was not given that opportunity. Both fights happened in Korea.