Size and capacity
You'll need to choose a food processor that's large enough for your home. Most models have a bowl capacity of between 1 and 3 litres.
It's also a good idea to check the specs sheet for the dimensions of the processor. If you've only got limited bench or cupboard space to work with, size really does matter. The weight of the unit is also important if you'll need to put it away in a cupboard for storage purposes.