The difference is that if 9 people watch 99 hours of A's let's plays or last 2 music videos on repeat, and one person watched 1 hour of B's 20 well-researched and edited 3-minute educational videos, A-watchers put in $90, B-watchers put in $10, and under global popularity A gets $99 and B gets $1. Local pooling would mean that A gets $90 and B gets $10. This is my main complaint against Youtube Red too.