Window AC consumes more power than split AC..The reason many be due to technology and as now-a-days most of the AC come with less power consumption technology ...cannt say that exactly...
According to my knowledge window A/C consumes more Power than split.
The reason why window A/C consume more power is because in window there will be one way circulation of air so that the compressor will be on for a long time for cooling the whole room.
where coming to split it has 4way circulation of air and it will not take much time the room will be chilled in a very short period.