Power consumption open collector/drain
A CMOS input (for example, VIN in the circuits above) does not source or sink any current (except for a little bit when switching), so when a push/pull output is connected directly to an input, no power is consumed for either low or high signals.

If the output does not drive another CMOS input but a load like a LED, then a push/pull output and an open-drain output would consume the same amount of power.