I'm never sure about this one. I judge them based off champions, rankings, forcing mandatories, stripping belts (for the right reasons) and also just sticking to the rules.
I think the WBC has the strongest champions but I also think they are the most corrupt (stripping Martinez and giving Chavez the belt, and stripping Ward was just stupid) also they are they do the dumbest things like open scoring and no unifications (but they allow it if the guy earns the most money in the division)
I think the IBF has decent rankings and they seem to be good with forcing champions to fight their mandatories, but they have a weak crop of champions.
WBO has some good champions and doesn't do anything that upsets me too much.
WBA loses its case for being the best automatically because it has 2 champions per division which is just insane.
I'm aware they're all bad, but this is only in comparison to eachother