I have owned or extensively used all the Canon macro lenses, bar the 180mm version.
My favourite macro lens?
The Sigma 150mm F2.8 with OS.
It's the sharpest of the lot, the OS is very handy and the bokeh is gorgeous, as is the colour and contrast.
The 100L is also excellent, but the Sigma is just a liitle better, and because of the extra reach, you don't need to be on top of the bug you're photographing, and the extra distance also allows you more lighting options.