If I understood correctly the question, what you are asking is
Why does an iron get so much quicker hot and reaches a higher temperature, compared to the heat pump that has a higher power rating?
Although the technologies are quite different (i.e. the resistive elements transform electricity to heat, while the heat pump transfers heat energy from a cooler room to a hotter room), the main reason that you perceive this, is the compactness of the heat surfaces.
The iron has a much smaller area compared to the power, so it is able to heat the ironing surface much quicker.
At the same time, the heat pump of an aiconditioning, has to warm up/cool down all the masses before being able to transfer heat.
Another thing is that the iron has a guaranteed power output (depends only on the available electricity), while the air conditioning heat pump will also depend on the relative air temperatures.
However, for a given room a resistive element of 5kW and a heat pump of 5kW, they should warm up the space in the same average rate. The main difference will be that the resistive element at 5 kW will start warming up the corner where it is placed, while the heat pump will have better circulation and warm the place more evenly (but less perceivably).