Pacquiao without a doubt.
"Legacy" is how you're remembered by the public, and Manny is viewed in a far more favourable light even in the States.
And if we're talking strictly boxing, Pacquiao is ahead of Floyd as an ATG as well. Don't give me this bullshit about how Floyd is undefeated, when anyone with eyes knows that he clearly lost to Castillo, and arguably lost to De La Hoya and Maidana too.
In the end, Floyd's legacy will be that of a cherry-picking, pillow-fisted, narcisstic domestic abuser while Manny's will be that of a humanitarian who overcame the odds many times and always put on exciting fights.