canon 100mm macro l vs non-l

I am looking in to buying the 100mm macro lens for my canon 6D, does anyone knows if the L version is significantly better in image quality? I know that the L version has IS, but since I will be shooting in daylight and the lens is fairly fast I don't think I will miss it.

Also I am just starting In macro photography, so any advice is appreciated. is it worth it to get a ring flash? any recommendations for that?