Geothermal energy or air heat, experiences?

Hello,
I have already read quite a bit about the two aforementioned possibilities as alternatives to gas.

Now I would like to hear personal experiences.

Geothermal energy:
I know that it is quite expensive, which is not a problem for us, but the following questions came up:
- Is the technology really mature?
- How susceptible is the technology according to your own experiences?

Air source heat pump:
This is supposed to be cheaper, but you often hear that it is quite loud.
I know similar units from the USA, but as air conditioners, and they were quite loud.
- Does the noise bother you?

I am curious about what you can name as pros and cons of both systems.

Thanks to you in advance!

I decided on a ring trench collector as a self-installation, so I get geothermal heat from the area. Due to the self-installation and the BAFA subsidy, I almost reached the price of an air source heat pump.

Regarding personal experiences, you will almost always hear the same from the builders: Mine is the best.

Geothermal energy:
I am aware that it is quite expensive, which is not a problem for us, however the following questions arose:
- Is the technology really mature yet
- how prone to failure is the technology according to your own experiences?

Air heat:
This is supposed to be cheaper, however one often hears that it is quite loud.
I know similar units from the USA, but as air conditioners and they were quite loud.
- Does the noise bother you?

The technology of the heat pump itself is initially the same, the difference lies in the connected heat source.
Here, I see an advantage in geothermal energy due to better, year-round efficiency. The probe itself is a passive, dumb thing embedded in concrete. What could possibly happen to it? Maybe topping up the brine every few years, but otherwise?
The outdoor unit of an air-to-water heat pump takes up space and affects aesthetics and noise. Although I don't want to overdramatize the latter, as long as the worst clunky device wasn’t purchased. The component is active, has moving parts and is exposed to the weather. In contrast to geothermal energy, I therefore see a higher likelihood that replacement will be needed at some point and maintenance must be performed.

In our area, there is no gas, so everyone has a heat pump. I would say 60% air-to-water heat pumps, with about a 50/50 split between indoor/outdoor installation, and 40% brine-to-water heat pumps with probes. We also have the latter.
After calculating the current subsidies, that was maybe €2000 more expensive than an air-to-water heat pump. The arguments above were more than enough to convince us of this option. The appearance on the building alone was worth it to me. You don’t need to calculate consumption costs, but as soon as a replacement is due, I can continue to use our heat source; an air-to-water heat pump will likely have to be completely replaced. At the latest then, geothermal energy is ahead. But the future will tell.

More important than the heat source is the quality of the planning: sizing, heating surface calculation, hydraulics without buffer storage, no individual room control.

That is what I would primarily focus on in your place. A well-planned air-water heat pump outperforms an average planned ground-water heat pump.

I would recommend the ring trench collector + subsidy if feasible, especially in cold regions. Price/performance is unbeatable. Ground source can sometimes cause problems; with an air-water heat pump, a solution in case of problems is usually significantly easier.

With our air-water heat pump (without indoor unit) I have the best experience, inaudible inside even though it is right in front of two windows. From about 3° it becomes slowly audible outside. If the neighbor is very close, you have to deal with the noise and choose very quiet devices or take other construction measures.

Compared to a ring trench collector, our air-water heat pump uses estimated 50€-max 100€ more electricity per year.

In the end, it depends on how much personal effort/planning is possible or what offers you receive.

Thank you for your comments

I am also just at the very beginning and sometimes still feel really overwhelmed and have to constantly google some technical terms

Can you recommend a good homepage where you can get a good introduction, especially at the beginning?
I have the feeling that I haven't found the right site yet....
Thanks to you all in advance!!

Google search for "in einer Wärmepumpe brennt kein feuer" or "Aquarea Club"