Which is better than commercial gas boiler brand viessmann and Dong Qing Nabian?

I am engaged in the HVAC industry. It is said in the industry that wiesmann has only done a good job in marketing in China, but the performance of their commercial gas boilers is actually not so good. For example, the internal structure of water conservancy components is made of engineering plastics, which is very messy, which is not conducive to after-sales. However, the performance of commercial gas boilers in Dong Qing is much better, and the internal wiring and layout are clearer, which is also very convenient after-sales. It has been widely used in nursing homes, commercial and residential apartments, hotels, office buildings and other large places.