What is the difference between piezo and pneumatic valves?

Pneumatic valves and electric valves, although the same belong to the dispensing valve, but there is a big difference, for example, I know of Leica piezoelectric valves through the electric pressure to promote the medium dispensing, pneumatic valves through the gas piezoelectricity to promote the medium dispensing, piezoelectric valves is an upgraded version of pneumatic valves, piezoelectric valves compared to pneumatic valves have a better degree of precision, but also more suitable for tiny dose of dispensing, but the price is expensive compared to pneumatic valves to be a little more expensive.