Is a geothermal heat exchanger better than a ventilation system with heat recovery?

I have to ask again. How much does a geothermal heat exchanger really bring compared to a simple ventilation system with heat recovery? How long should the ground pipes be and is it also worthwhile in summer?

"Erdwärmetauscher better than" is not quite correctly phrased, "in connection with" is more appropriate.
The ground temperature does not fluctuate as much as the air temperature and from about 80cm depth it is considered frost-proof in our latitudes.
Just google ground temperature.

How much does a geothermal heat exchanger really bring compared to a simple ventilation system with heat recovery?

See pictures: Outside temperature: 3.9°C -> Geothermal heat exchanger -> Temperature at ventilation system intake 14.1°C -> Heat recovery and heating = Indoor temperature 21.6°C -> Heat exchanger -> Temperature at ventilation system outlet 20.3°C

How long should the ground pipes be

My research some time ago resulted in about 30 to 50 meters per pipe. Because of residence time, or heat transfer and pressure drop.

and is it worth it in summer too?

If you google ground temperature, you see that the ground temperature is also capped upwards. As a result, the indoor air heats up somewhat less during the day in summer.