PER is notoriously correlated with USG though; a 31 FG% player will see better PER just by taking more shots. BPM isn’t as bad but it is distinctly worse than the WS and WP methodologies. This is relevant because we know the four accepted candidates do not have equal USG; for example, LeBron’s PER is 4 points lower than Westbrook’s but his USG is 12 points lower. This could spiral into a long debate about usage-efficiency curves, team building, etc., but the main takeaway I hope we can agree on is that not every composite stat has the same answer to parsing volume and efficiency.