Way back when Metro would get to crush levels during rush hour, it wouldn't be uncommon to see one train absolutely brimming with people still trying to squeeze in, and then the next train be completely empty. If you saw the next train was 3-5min away and was not crowded, you may consider taking that gamble to wait for the next train for a more pleasant commute.

Also, someone who rides regularly probably knows which car to get onto that is closest to the exit at their destination and where that car stops on the platform. However, if the train is crowded, they may opt wait where a less popular car stops, like the first car since they tend to be further away from station entrances.