Hi Vic,
Thank you for your intervention on this subject,
In fact, I would keep the Canon 100mm Macro because for me, it's the best existing macro lens because the image quality is superb, and it had a great versatility in use. This one is a fantastic tool !
I'm totally agree with you.
Having a second macro lens with a large focal length, would more readily approach especially for certain species of butterflies and dragonflies.
The fact that it would be a stabilized lens to my utility because I never use a tripod because it is too bulky in my opinion. And very often, I'm lying in the grass and I really didn't want this equipment that I believe would prevent my reactivity and my approach.
I know that the optical quality of Sigma is generally less clean but ... In all honesty, at this level it is not dramatic.