I think Pac is more likely to get a decision than a KO.
I agree that Psc's KOs come against fighters with a 'come forward' style or when he's juiced to the gills or both.
Since Mayweather is not going to walk himself face first into Manny's fists and assuming the drug testing prohibits Manny's habit of PED use, then I rate Pac by decision higher than Pac by KO.