I haven't had any experience with a Mazzer, but I've onwed 2 Macaps, one being a doser M4 and an M7D. They're both good grinders, but for different reasons.
I think that you hit the nail on the head when you mention that no one favours one over the other, they're both superbly manufactured grinders and will give you a lifetime of use if they're looked after. I think the decision between the two would come down to personal preference in relation to use and looks.
When you say that you're after feedback from people who use these grinders in a commercial environment, do you mean those that use your target grinders (Mini or Macap M4/5), or other model grinders from these two manufacturers?
As for recommendations where to buy, there's a few site sponsors in Sydney and one in Canberra who I'm sure would be able to take care of you. Make sure you try each grinder out, you might find the ergonomics of one suits you better over the other.
All the best with your purchase and if you need any more help, please question away.