So the question is what makes this style unique and distinct from all other styles?

It emphasizes girly-ness under many various categories. Curls are a must especially when going for a hime (princess) gyaru look. They oftentimes tan, both manba and yamamba categories have the darker tan with the white around the eyes. The pictures i posted are of some foreign gyaru, some well known like Pin (red hair) others not so much, but they all demonstrate that although styles originate from a country outside of theirs, they've embraces it and emulated it so well, they've found what they like. Essentially what fashion should be , an outward expression of what you like and enjoy wearing (note: none of these pictures were professionally taken with the exception of sakurino)