There are two clarinet systems today: The German system and the Boehm system. The following description does not crown a definitive winner, but merely highlights the characteristics of each system.
The German system is more widespread in German-speaking regions than the Boehm clarinet. Clarinet teachers are more familiar with the German system and often recommend it. If you aspire to be a professional clarinetist in Germany, the German system is the way to go. However, if you want to perform on international stages, you should consider the Boehm system.
It's important to know that not only is the sound different, but also the fingering. Relearning is possible, but it involves not only a slightly different approach but also different fingerings.
But how can a beginner tell if the clarinet in front of them is German or French system? The first glance reveals it: The Boehm system uses levers instead of "rollers" for the little fingers on the long keys!
In terms of the number of keys or structural features that distinguish the two systems, the following chapter explains further:
The main feature of the Boehm clarinet is its number of keys. The variety here is not as extensive as in its German counterpart. Typically, a Boehm clarinet has 17 keys and 6 rings, or even 18 keys and 6 rings. Minor variations are possible, but there isn't a progressive list of keys like in the German system. The key configuration allows players to master challenging passages with special fingerings, even without additional keys. In terms of fingering, the clarinet can be compared to the saxophone due to its key style. From a fingering perspective, transitioning to the saxophone later is much easier.
Ideally, the number of keys on a German system clarinet increases with the player's abilities. It's important not to make the mistake of assuming that every year a key is added for another finger. It also doesn't mean that the clarinet is like a construction kit. Adding new keys also means buying a new clarinet! The number of "main keys" does not change, but auxiliary keys, trill keys, and special keys for specific tone combinations are added. But when is it enough? Clarinets produced in series typically have a maximum of 25 keys, 5 rings, 1 thumbplate (or 6 rings and no thumbplate), and 4 trill keys. Fingering-wise, the German clarinet is similar to the Baroque recorder system. Those who play the alto recorder, for example, can transfer some fingerings to the clarinet. This is particularly helpful in the lower register at the beginning of the learning phase.