[Rainer]

My first question would be, why would you prefer

a 150/180mm macro lens over a 100mm macro lens?

Is this for the distance to the subject?



In that case, let us have a look on the effective focal length that these lenses

have at MFD (minimum focus distance).



The Sigma has MFD of 38cm and has a focal length of 95mm there.

The Tamron has MFD of 47cm and has a focal length of 118mm there.

The Canon 100L has MFD of 30cm and has a focal length of focal length of 75mm there.



So, regarding the focal length I would prefer the Tamron over the Sigma.



On the other hand, if you look especially for the support of in-lens image stabilisation,

I would really have a look on the EF 100L (especially, since the price for the Sigma is

quite bold as well).



In all, I believe that with macro-lenses you don't really make a mistake regardless

which one you take. They are all quite good.



Just my 2cts ... Rainer