From which manufacturer should you buy the heat pump - ventilation system combination?

These are all brand manufacturers. So far, I have had Waterkotte, Vallox, Panasonic, Raumluftshop in operation myself. They were all "good." Some have advantages in the software (Panasonic, for example, is totally relaxed in terms of the user interface because there are simply no complicated menus), some are a bit more efficient than others, etc. There are no bad apples. Besides that, there are smaller providers where you would need to do research (in forums or similar).