This is a decision Im weighing up at the moment also. Having used both the Robur and K10 (non WBC) recently, hasnt helped the decision. They both have their positives and negatives.
In regards to your criteria, I would say both grinders meet all except for 4. The Robur is a fair bit dearer than the K10.
The other thing would be weight. The Robur is built like a tank and wouldnt be too easy to move around. Whereas the K10 I imagine would be lighter and easier to transport.
The other problem with the Robur; for me anyway is that it shows up how short I am. It kind of leans over and pats me on the head condescendingly. :)