I have used both. But that's OK.
When and for how long? Which lens do you have now? If you have/had both, why didn't you speak from personal experience originally, rather than refer to other discussions?
You're need to be right exceeds mine.
My ability to spell "your" correctly within the context of the above sentence also exceeds yours.
Regarding the merits of the new lens versus the old lens, the new 100mm macro simply
is superior to the old one, in many respects, by all accounts and by all tests. At best, the old one merely "equals" the new lens in some respects, but in many other respects the old lens simply falls a bit short of the new.
Better MTF scores = better MTF scores. Better image stability (by up to 4 stops) = better image stability. Look up the word "tautology" (in the logical, not rhetorical, sense) when you get the chance, as it is the most basic principle of math and logic: A = A; better = better.
The only area where subjective opinion enters is whether or not it is "worth it" to make the switch. IMO, and in Bart's opinion, it
was worth it. In your opinion, it clearly was not. Your statements that people such as we (who believe the upgrade to be worth it) "feel the need to defend the lens" are ridiculous. We simply feel that the upgrade was worth it. The real question is why do
you "feel the need" to downplay the tested facts and our honest opinions as to our preference for the new lens?
The truth is, the new lens
is superior to the old one in many respects, all of which have been measured and quantified with relatively-consistent results. The other truth is, regarding whether it is "worth" upgrading or not, in the end this is an entirely personal opinion. You have made your opinion known, so please allow us to make ours known. Ultimately, it will be up to the OP to make his own decision, based on his own wants and needs, all of which will be different from both yours and mine.
If you want a Macro lens that also is great for portraits the Canon 180 makes either of the 100s pale by comparison.
I am not sure this subjective opinion is supported by any tests or facts, but it is outside the discussion topic. Further, even if this were true, the asterisk to your statement would be ...
provided you have the room to use it ...
Have a great one K.C.
Jack
.