What is the difference between ceramic and washerless cartridge?

Both are very distinct systems.

A ceramic cartridge depends on two opposing discs with triangular openings which either line up to allow the flow of water or block the opposing disc openings (preventing the flow of water).

A washer-less cartridge is designed with a stainless steel plate at the bottom. This has a crescent shape cut out as the cartridge rotates the cutout lines up with a spring-loaded washer to allow the flow of water. When the cartridge turns 180 degrees, the spring-loaded washer will line up with the solid portion of the cartridge blocking the flow of water.

YouTube Channel Video: What Are Two Types of Cartridges Offered by Kingston Brass

The bottom line is that both systems perform the same function in a consistent manner. The major differences are that because ceramic cartridges will not wear out due to friction. The ceramic cartridge, however, is brittle and any debris on the water lines may cause the cartridge to crack or disengage. On the other side, the springs on the washer-less cartridge will eventually lose their tension allowing water to seep in between the washer and the stainless steel plate causing the faucet to drip. Should repairs be necessary, replacing the springs, washers, and cartridge is far more economical than replacing a ceramic cartridge.