Technically convinced me the excellent interaction with our Fritz! Box 7390. The recruitment and customization options are top notch. Commissioning, operation and performing updates are also extremely easy. The (very good) manual you do not really need, because the menu is self-explanatory.
But all these advantages come to the fore only when you use a Fritz! Box as a base phone. If you use the Fritz! Fons as a secondary device for other phone stations, all the settings can probably not be used.
For voice quality I can not say anything negative, although our Fritz! Box is in the conservatory, which shields structurally well all radio waves, we have a very good connection with clear, low-noise sound.