They are basically the same principle except the neon gas both lowers the trigger voltage and makes it predictable. Neon bulbs must operate within power limits while spark gap power is only limited by physical size and material.
Spark gaps are etched into PCBs all the time to provide some protection from surges. Unfortunately PCB and air spark gaps exhibit widely varying breakover voltage dependent on gap, temperature, humidity, contamination and altitude.?Spark gaps should never be placed across an AC or DC line. If the line voltage is high enough, they effectively become a short once triggered.
