I have a Kmix so the food processor is an attachment that goes on the end of the immersion blender. I use it for crumble topping (one part sugar, one part fat, two parts flour), pastry, making my own nut butters, grating cheese when I need a lot, making my protein baked goods (generally sloppy and needing mixing in a blender), making fish paté, making bean patés
I find 1litre is quite enough for my needs.