If you make a lot of:
Get a KA
On the other hand, if you make:
Large quantities of sauted onions
Get a food processor.
Personally, I find that other than making the best pie dough on the planet, food processors aren't the perfect tool for much. They'll grind meat, but not that well (it's easy to overgrind it and you have to cut the meat carefully before you begin). They'll knead dough, but again, no where near as well as a mixer. They'll make mashed potatoes, but not as well as a ricer or a potato masher. They'll slice veggies, but in order to make the cleanup worthwhile, you have to slice a LOT of veggies. They're great for pureeing soups, but a hand blender does the job just as well, at a much cheaper price. For grinding things such as red curry paste, a blender is far superior. Pie crust, that's the only application I can think of where a processor is the clear cut best choice as the blades not only cut the fat into the flour, but they cut the ice water in as well, resulting in minimal gluten formation.
I've been meaning for some time to pick up a thicker slicing blade. Maybe if I had that I'd do more veggie slicing.