Geothermal is often better for heating than cooling. The main reason for this is that in most climates, it's easier to extract heat from the ground than to extract cold from the ground. In other words, the temperature of the ground below the surface is usually warmer than the air above the surface. So in winter, it's easier to use geothermal energy to extract heat from the ground and warm up your house, than it is to use geothermal energy to extract cold from the ground and cool down your house.