Blenders are not the most popular thing on the kitchen counters of today. In fact, the presence of a blender, even one hidden deep in some obscure cabinet, is sometimes cause for chagrin on the part of sophisticated cooks. "Yes, but I never use it," they are quick to say.

But the fact is that blenders do several things much better than food processors. This may not be reason enough for most people to rush out and invest in one, but it could be reason to get the old Waring out of mothballs.

In commercial kitchens, blenders are called bar mixers, and it's with squishy things like iced drinks that blenders got their start. Things began going wrong for the poor machine when it hit the home-kitchen market awash in claims that it could do everything but the dishes.

A blender won't chop onions or grind meat or mix and knead bread dough as a food processor will. But for anything involving aeration or emulsification, a blender is tops.

Compare salad dressings, for instance. Unless you are making vast quantities, the food processor will leave pools of oil on top of the dressing, the solid matter having been pasted to the bottom of the bowl. This is especially true if you make dressings that include garlic, fresh herbs, anchovies or mustard. Even the smallest quantities of dressing -- just a few tablespoons -- will be perfectly emulsified in the blender.

I also prefer the blender for pesto and other thick sauces -- walnut-garlic sauce for pasta, for example -- because of the way the ingredients are perfectly blended. Of course the purist's way with pesto is by hand, but for cooks who need mechanical help, the blender is better.

The gigantic bowls of today's best food processors look as if they hold more liquid than they actually do, with the result that the over-ambitious cook sometimes finds the pure'eing zucchini soup around, under and over the bowl but not in it. While liquids will slosh out of the blender container if you fill it too full, the configuration of the blender is made to hold liquids.

There are other, more esoteric reasons for the blender's existence. One friend says she tried to pure'e prunes and armagnac as a preamble to making ice cream, and noticed the prunes hiding, flattened out, between the blades and the bottom of the bowl. She switched to a blender (she had to borrow one) and voila , the prunes were mush in no time.

Some pastry cooks don't like store-bought confectioners' sugar because it contains cornstarch, so they make their own. You can do this in a food processor by whirling granulated sugar around, but I like the blender better because it makes an even powder instead of dust and granules. The same goes for bread crumbs in my estimation, but there are people who argue about that.

The icy-mush fruit drinks that blenders were so good for are no longer fashionable, but if they ever come back, those of us who didn't let our blenders go at garage sales will be grateful.

If icy-mush drinks are a big favorite in your household, however, think about a commercial-quality blender. The differences are these:

Commercial blenders have more powerful motors, so they last longer. Greater quantities of tough stuff like ice cubes (always with a little liquid, even in a commercial blender) can be crushed at one time without burning out the motor.

The workings of commercial blenders are more likely to be metal and therefore less likely to wear out, bend or break.

Capacity is likely to be larger in a commercial blender. One popular model sold by E.B. Adams, a restaurant supply and equipment house at 1612 U St. NW, is the Hamilton Beach 44-ounce version with a very tough plastic container.

Commercial blenders generally only have two speeds, which, if you think about it, are all you ever use anyway. The eight or 10 speeds found on most home mixers just add buttons and extra mechanical trouble, not versatility.

If you are interested in a commercial-quality blender, shop around for the best price. Some supply and equipment houses will not sell to the general public, some will at prices slightly higher than what they'd charge restaurants, and some will with no restrictions. E.B. Adams charges just over $80 for the plastic-container Hamilton Beach.