Both can drop a flame in seconds. Only one of them stops the grease from reigniting the moment the powder settles.
Dry chemical agents — sodium bicarbonate, potassium bicarbonate (Purple-K), monoammonium phosphate (ABC) — are genuinely effective, fast-knockdown agents on a wide range of flammable-liquid and electrical fires. Wet chemical agents — typically a potassium acetate, citrate, or carbonate solution — are slower to apply and built almost entirely around one specific fuel: hot cooking oil and fat. Confusing the two, or treating "it's a chemical agent that puts out fire" as a single interchangeable category, is exactly the mistake that UL 300 exists to prevent. The two agents don't just differ in strength — they extinguish through fundamentally different mechanisms, and only one of those mechanisms actually addresses why a commercial deep fryer keeps trying to reignite itself.