Both devices do their job without problems.
The only differences I could find - in addition to the extra bottle at SEVERIN - are in my opinion the design and activation of the mixer.
The WMF equipment is kept in the typical colors of stainless steel and black. When the bottle is screwed WMF device in the device. Only then you can switch using either short pulses or if you continue down the key lasts longer mix. We the button is not pressed not mixed.
The SEVERIN device is kept light green and white. I thought initially that it would possibly look cheap, but it's well made. When SEVERIN device, the bottle is placed on the engine. If now the bottle is pushing down mixed until the bottle releases (pulse function). If you hit the bottle down and the mixer mixes, you have the possibility tighten the bottle and can you release it and it will continue until the bottle is mixed unscrewed again.
The bottles are interchangeable. So you can screw the SEVERIN bottles on the WMF cutting tool and vice versa.
This is very handy if you want to purchase additional bottles.
I then decided to use the WMF product because it color fits better into our kitchen, but I will organize my extra bottle of SEVERIN.