... bringing this up again only because there are 330 views... (of which I'm 3 OR 4)
Just ran a test of the two Jax products on some 6-penny nails. Polished with 400 grit wet/dry paper (dry), applied both until they turned black and rubbed off with a blue shop paper towel. Both performed similarly and left a very even light grey finish.
Still not sure what the difference, if any, might be between them. For my goal, at least, it seems either will accomplish the finish I'm desiring.