C.C.
I have not used the KitchenAid, but I have the Cuisinart Elite 14-cup. I love it. I haven't found a single thing it can't handle yet, to be honest. It has a 1000-watt motor, so it has plenty of power for just about any task. What I really like about it is that it has 3 different bowl sizes - 4.5 cup, 11 cup, and 14 cup, plus a bunch of slicing discs, shredding discs, and several different blades. So it is very versatile. I can put frozen steaks into it in 2" cubes and have ground beef in under 10 seconds. I can put a tablespoon of oregano leaves in the small bowl, and it will mince them. Basically, it can handle the brute force tasks as well as the finesse tasks.
Originally, what I *really* wanted was the Robot Coupe r101, but it costs at least $200 more than the Cuisinart, and the Cuisinart provides a similar result for my level of cooking (I would say that I'm advanced, but probably not expert ;).
My only complaint about the Cuisinart is that for dicing, I still need to do a little knife work myself after the item comes out of the Cuisinart (for instance with onions), if the precision of the dicing matters in the recipe. I have not been able to master the technique for getting it to dice evenly but finely. I have friends who somehow make it work, so the fault may be mine and not the machine's. The other minor complaint is that it is a little bit tall to fit underneath my kitchen cabinets. I have to take the food pusher out of the processor in order for the machine to slip underneath the cabinet. In reading the reviews on Williams-Sonoma, I see I am not the only one with that issue. (If you have an appliance garage, then of course that won't matter.)
Anyhow, overall I feel like the Cuisinart 14 has been worth every penny.