One is tall and thin and quite racy, like some people we know, and the other is short and stubby and a real workhorse, like, well,… never mind.

Bad generalities aside, blenders and food processors have areas of overlap, but each also performs tasks at which the other is not brilliant. In general, blenders are better suited to working with liquids (they are also called liquidizers or liquefiers), and food processors work wonders with more solid foods. Of the two, the food processor is the more versatile.

The fairly tall, narrow container of the blender, the short, angled blades, and the motor speed are what sets it apart. It was invented in the 1930s by F.J. Osius, whose patent claimed it would "produce fluent substances." He showed it to the big band leader Fred Waring, who took such a shine to it that he formed a company to sell it and took it around the country when he traveled with his band, along with a portable bar to demonstrate its prowess at mixing drinks. Burt Wolf says in The New Cook's Catalog that Waring once use it to make 400 daiquiris at a single cocktail party.

To this day, blenders see a lot of use behind the bar. They are is also used in the kitchen to purée, emulsify, blend, and grind. They are wonderful for pureeing soups, liquefying fruit, blending drinks (smoothies and milk shakes, as well as those wicked alcoholic concoctions), chopping ice (although some inexpensive models are not up to the task), and smoothing and emulsifying sauces. They also work well for chopping bread crumbs and herbs. The blades can turn at speeds up to 18,000 revolutions per minute.

The food processor began to find its way into home kitchens in the 1970s, and perhaps its leading claim to fame is that it allows you to perform many tasks much more quickly than can be done by hand. Many models have interchangeable blades and disks - for shredding, grating, slicing, and kneading dough, although 90% of the time, you'll rely on the S-shaped chopping blade. The food processor excels at slicing, shredding, chopping, and pureeing fruits and vegetables, grating cheese, grinding stale bread into crumbs, cutting butter into pastry crust, and kneading bread dough. It will cream soups, but will not get them as silky as a blender. With some soups and purees, you may want to pass the mixture through a strainer after processing. Most models work at a single speed, which is slower than a blender, but have a pulse function that gives you greater control over the chopping/kneading/cutting processes.

Finally, although not perhaps officially part of your question, immersion or hand blenders were introduced into home kitchens in the 1980s, although they had been in service in restaurants for a couple of decades already. Shaped like a wand, they bring some of the emulsifying and pureeing power of the blender to the container or pan of your choice. A benefit is that you can blend larger amounts of food than will fit into the jar of a standing blender. Home models tend not to be as powerful as stand blenders.

The question of what you need in your kitchen is, quite happily, yours alone to answer. There are those who scoff at the introduction of any labor-saving device in the kitchen. Anything you can do with a food processor or blender, you can do with a good knife and cutting board, whisk, wooden spoon, strong right arm and unlimited time, they say, as their forebears did for centuries. But for those whose time is limited, both appliances make it easier to get dinner on the table, to entertain, and to do so with more variety. If you have to choose between the two, our vote goes to the food processor, because it is more versatile. If you can afford both and have room in your kitchen (and dishwasher or dish drainer, where the parts seem to be omnipresent) for both, you'll put them both to good use.