This tends to be called comparative advertising in America, but here in Britain it's called knocking copy.
Knocking copy is an advertisement which compares its product favourably with another brand. This other brand might in the past have been called BRAND X, but nowadays is more likely to be named a (or the) leading brand.
Contains twenty per cent fewer calories than the leading brand. That kind of thing.
Eight out of ten owners said their cats preferred it is a more subtle and oblique example.
Adverts are hedged around with laws and regulations, nowadays, and firms have to be very careful with their knocking copy.
It's rather a shame. Life would be livelier if advertisements said things like:
Drink BONGO: because BINGO tastes like cat sick.
Word To Use Today: knock. The Old English form of this word was cnocian. The Old Norse knoka means to hit.