I like #20 much better than #19. It has more of a 3D effect like it is a tube. However, I think it looks more like a neon light than an LED trace. I'd like to see less glow, or maybe just not as strong of a glow? I've been looking through different light graffiti pictures and I think what I want that seems to be missing is that the sine wave is too perfect. The way the light is in the photography there are bursts or surges of light, some are more obvious than others, but THEY seem to be the reason for the glow. I think that there is still more to do to make the wave look right. I am uploading a new picture that has more of a 'wave' in the graffiti that might be helpful.
As far as other changes, I'd like to see more of a round font for the name. I think that since the sine wave is so curvy, the font needs to be a little less 'techy'. It is rounded, but I think a font more circle based would be better. I think it would also help the 'A' and 'M' in the mark stand out if the 'A' and 'M' in media were similar. I would also like to see a little more distinction between 'ambient' and 'media', by altering their colors slightly. Not by much, just a little. Also, could you make 'inc' just a smidge larger? It is hard to read, and I'm afraid on a business card, you wouldn't be able to see it at all.