The answer behind the success of Miele relies on the good design based mostly on previous experiences and the level of technology they offered in their product. One of which is their HEPA Miele vacuum cleaner bags and belts and filters which is very efficient in trapping even the tiniest of microscopic particles as well as dust mites, the eggs dust mites lay, pollen which can trigger allergic reaction and many other health complications.
Other people claims that they are equally the same since some of the materials used in Miele products came from various third party sources who specialized in their particular field. For example a dishwasher that is manufactured by GE, if you examine it carefully employs a different brand name of belt, also with many other dishwasher parts and you could basically get a substitute GE appliance parts directly on the 3rd party manufacturer and it will still work properly.
If you are a big fan of authentic Miele parts, you should look at the labels or inquire the vendor because they are often confusing and appears really the same. Before finally making the order you have to look at the item description carefully, look for the compatible models that it can be fitted to prevent any trouble of returning it if you ordered the wrong one.