Side-by-Side Demonstration

Commercials for common household products will sometimes have a demonstration of the advertised product's effectiveness compared to another leading brand—either Brand X or an actual competitor.

The demonstration is usually done by showing both brands being used side by side, with the ad's brand being far more effective, lasting longer, doing more, etc.

In the US they can and will mention the competing brand by name. In Canada, the UK and Australia this is not allowed, so the other brand is usually referred to just as another leading brand.

Dish detergents often do this, with stacks of dishes, grease cutting power of a single drop, scratched glass, etc.
Laundry detergents demonstrate the amount of clothing they will clean, or will show a bright white shirt next to a dingy Brand X-washed one.
Battery ads will do this with how long they last.
Common with absorbent products such as paper towels, diapers, tampons, and women's pads.

In Germany, it is actually illegal to say anything disparaging about a competitor's product, even if your statement is true. So, if your product is healthy and you know your competitor's product has additives that cause cancer, it's against the law to say this in an advertisement in Germany!

In France, it used to be illegal. Not anymore, but you can only do this if you have studies with numbers backing your claim.

When things are being shown absorbing liquid, especially diapers, tampons, and pads, the liquid will be blue. Understandable, given that it's highly visible and no bodily fluids are blue—red, yellow, or brown liquids seem fairly disgusting.

Compare Too Incompetent to Operate a Blanket for those side-by-side demonstrations where one side is performed in an obviously ridiculous fashion.

Examples of Side-by-Side Demonstration include:

The Metamucil fiber supplement demonstrates how easily it dissolves in water compared to its competitors.
Tylenol soft chews are cut in half next to a pill of the common, hard kind.
Pampers diapers are shown absorbing more blue liquid than another brand.
- Tampax tampons do this as well.
- So do Always pads, and their "lock-away core".
A finger with a drop of Dawn dish detergent is shown being dipped into pans filled with greasy water. The grease immediately springs away from where the finger touched the water. Dawn always gets more pans than the competition.
Duracell had a well-known commercial in which a fleet of "battery-powered" toy rabbits with snare drums using the "leading brand" would run down, while only the rabbit containing a Duracell battery kept marching. Turnabout being fair play, Energizer reproduced the commercial, with a voiceover explaining that this result was only because their brand hadn't been invited to the competition—at which point a larger and much flashier toy rabbit with a bass drum marched across the screen. The Energizer Bunny would go on to become a Mascot, starring in a number of Commercial Switcheroo bits.
Subverted—much to the manufacturer's likely chagrin—on the earliest Bob and Ray shows. During a stint with a floorwax sponsor that asked them to urge customers to make a side-by-side test on their own floors, Bob once inquired mid-commercial, "Uh...if we're so sure they'll think [sponsor's wax] is better, why should they bother doing the test?"
Parodied multiple times on Monty Python's Flying Circus, with the American Defense/Crelm Toothpaste/Shrill Petrol sequence of cartoons, and Whizzo Butter, which 9 out of 10 British housewives can't distinguish from a dead crab when the two are placed side-by-side.
In an ad for a Swedish telephone company, the company's logo is featured on a greyhound, while the logos of other companies are featured on "slower" dogs. In later ads, the logos of the other companies are blurred out.
One advertisement for the Amstrad CPC was intended to show how much easier it was to set up than other home computers of the time. The other computer shown is shown from such an angle that the maker's name isn't visible, but from its color is a ZX Spectrum.