Without a doubt the added focal length would be beneficial so the Tammy is still under consideration.

Sorry for being so dense and maybe I am getting to analytical about this but could someone explain to me what this means on the difference in the two Canon 100mm macros as far as does it make a difference on use or IQ or does it just have to do with one having IS and the other not ...

100mm IS - Lens Construction: 15 elements in 12 groups
100mm non-IS - Lens Construction: 12 elements in 8 groups