Neon Flicker skips the installation and drops you at the moment a tired sign is struggling to hold its charge. There is no draw-on: the word is already there, cutting in and out at an uneven rate before it steadies.
A single flicker keyframe drives opacity through a deliberately unmusical set of stops, over the same feGaussianBlur + feMerge glow stack the other neon styles use. Because it never draws on, it is the cheapest neon style to render — useful when you are exporting long loops.
Neon Sign performs an installation — the tube traces on, fills, then pulses. Neon Flicker starts lit and simply fails intermittently. Pick Flicker when you want mood, Sign when you want a reveal.