The quote seems to be taken out of context so I think some clarifications are warranted:
My opinion FWIW is the iberital challenge grinder is NOT a light COMMERCIAL grinder but an excellent home use grinder. There is absolutely no reason why it couldnt handle 20 coffees a day if they were well spread out through the day, HOWEVER if I was doing 20 a day I would buy something quicker and quieter....to better match the kind of machine that I would use to do 20 a day, which certainly would not be a domestic end machine. Ergo, its about what you want to do in a day, and the kind of equipment you are prepared to live with. For 20 a day I would use a semi commercial and mate it up to a real small commercial grinder such as macap M2 or m4, mazzer mini, compak k3T, eureka mignon etc etc etc all of which are much more capable (ie easier to use / deal with) for......20 a day.
That said, the Challenge is an excellent ("top end" if you like) domestic grinder, the grind quality is there and repeating, its just slow and noisy (and therefore frustrating to use) if you want to produce "many" coffees in a sitting.
Without going into specifics, my opinion is, the Iberital Challenge is a much "better" grinder than the other mentioned in your question and if I were personally to have to choose between them, I would choose the Challenge.
Hope that helps.